Modal Verbs

Modal Verbs express necessity, ability, permission, or probability. Examples include 'can', 'must', and 'should'.

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Modal Verbs Introduction

Here's a list of the modal verbs in English:

can, could, may, might, will, would, must, shall, should, ought to

Modals are different from normal verbs.

They don't use an 's' for the third person singular.
They make questions by inversion ('she can go' becomes 'can she go?').
They are followed directly by the infinitive of another verb (without 'to').

Probability

First, they can be used when we want to say how sure we are that something happened / is happening / will happen. We often call these 'modals of deduction' or 'speculation' or 'certainty' or 'probability'.

For example:

It's snowing, so it must be very cold outside.
I don't know where John is. He could have missed the train.
This bill can't be right. £200 for two cups of coffee!

Ability

We use 'can' and 'could' to talk about a skill or ability. For example:

She can speak six languages.
My grandfather could play golf very well.
I can't drive.

Obligation and advice

We can use verbs such as 'must' or 'should' to say when something is necessary or unnecessary, or to give advice. For example:

Children must do their homework.
We have to wear a uniform at work.
You should stop smoking.

Permission

We can use verbs such as 'can', 'could' and 'may' to ask for and give permission. We also use modal verbs to say something is not allowed. For example:

Could I leave early today, please?
You may not use the car tonight.
Can we swim in the lake?

Habits

We can use 'will' and 'would' to talk about habits or things we usually do, or did in the past. For example:

When I lived in Italy, we would often eat in the restaurant next to my flat.
John will always be late!

Past Modals

The past modals 'could have + past participle', 'should have + past participle' and 'would have + past participle' can be confusing. That's why they have full chapter.

Modal Verbs of Probability

We can use these modal verbs (also called modals of deduction, speculation or certainty) when we want to make a guess about something. We choose the verb depending on how sure we are.

Talking about the present

must / might / could / may / can't + infinitive

For example:

I am waiting for Julie with another friend, David.

I ask: 'Where is Julie?'

David guesses:

She must be on the bus. (I'm fairly sure this is a good guess)
She might come soon. (maybe)
She could be lost. (maybe)
She may be in the wrong room. (maybe)
She can't be at home. (I'm fairly sure this isn't true)

Notice that the opposite of 'must' is 'can't in this case.

Will / won't

We use 'will' and "won't" when we are very sure:

She'll be at work now.

Should / shouldn't

Should and shouldn't are used to make an assumption about what is probably true, if everything is as we expect:

They should be there by now.
It shouldn't take long to drive here.

This use of should isn't usually used for negative events. Instead, it's a better idea to use will:

The underground will be very busy now (not: 'should be').

Can

Can is used for something that is generally possible, something we know sometimes happens:

Prices can be high in London.

Can is not used to talk about specific possibilities:

He could be on the bus (not: 'can be').

Talking about the past

must / might / could / may / can't + have + past participle

must have + past participle
might / might not have + past participle
could / couldn't have + past participle
may / may not have + past participle
can't have + past participle

For example:

You: Where was Julie last night?

David:

She must have forgotten about our date.
She might have worked late.
She could have taken the wrong bus.
She may have felt ill.
She can't have stayed at home.

Will / won't + have + past participle

Will and won't / will not + have + past participle are used for past certainty (compare with present use of 'will' above):

The parcel will have arrived before now.

Should + have + past participle

Should + have + past participle can be used to make an assumption about something that has probably happened, if everything is as we expect (compare with present use of 'should' above):

The train should have left by now

Could

We can use could + infinitive to talk about a general possibility in the past (compare with the use of 'can' above):

Prices could be high in the sixteenth century.

This is not used to talk about specific possibilities in the past (instead we use could + have + past participle):

He could have been working late (not: 'could be'. As this is a specific possiblity, 'could be' is present tense)

Modal Verbs of Ability

When we talk about ability, we mean two things.

First, we mean general ability. This is something that once you have learned you can do any time you want, like being able to read or swim or speak a language, for example.

The other kind of ability is specific ability. This mean something that you can or can't do in one particular situation. For example, being able to lift something heavy, or find somewhere you are looking for.

Present

can / can't (for both general and specific ability)

Should + have + past participle can be used to make an assumption about something that has probably happened, if everything is as we expect (compare with present use of 'should' above):

I can play the piano.
She can speak English.
He can't drive – he's too tired.
We can't come now.

Past

could / couldn't (for general ability)

I could read when I was four.
She could speak French when she was a child, but now she has forgotten it.
He couldn't dance at all until he took lessons.
My grandfather couldn't swim.

was able to / couldn't (for specific ability)

When the computer crashed yesterday, I was able to fix it.(not 'I could fix it')
She was able to pass the exam, even though she hadn't studied much.(not 'she could pass')
He called us because he couldn't find the house.
I couldn't open the window.

could + have + past participle (an ability someone had in the past, but didn't use)

I could have played the piano well but I didn't practise enough.
We could have come earlier.
She could have studied law, but she preferred to become a secretary.

Future

will / won't be able to (general ability)

At the end of the course, you will be able to make your own website.
He won't be able to speak Japanese in a week! It will take months.

can / can't (specific ability)

I can help you tomorrow
I can't come to the party

Modal Verbs of Obligation

We can use have to + infinitive, must + infinitive and should + infinitive to express obligation (something you have to do).

Present	Positive	Negative
have to / don't have to	strong obligation (possibly from outside) Children have to go to school. (sometimes 'have got to')	no obligation I don't have to work on Sundays. You don't have to eat anything you don't like.
must / mustn't	strong obligation (possibly based on the speaker's opinion) I must study today.	negative obligation You mustn't smoke here.
should / shouldn't	mild obligation or advice You should save some money.	mild negative obligation or advice You shouldn't smoke so much.

Present

Positive

Negative

have to / don't have to

strong obligation (possibly from outside)

Children have to go to school.

(sometimes 'have got to')

no obligation

I don't have to work on Sundays.
You don't have to eat anything you don't like.

must / mustn't

strong obligation (possibly based on the speaker's opinion)

I must study today.

negative obligation

You mustn't smoke here.

should / shouldn't

mild obligation or advice

You should save some money.

mild negative obligation or advice

You shouldn't smoke so much.

Be careful about the difference between mustn't and don't have to!

Mustn't means it's not allowed, or it's a bad idea:

You mustn't eat so much chocolate, you'll be sick

Don't have to means you don't need to do something, but it's fine if you want to do it:

I don't have to get up early at the weekend(of course, if I want to get up early, that's fine, but I can stay in bed if I want).

Past	Positive	Negative
had to / didn't have to	obligation in the past I had to wear a school uniform when I was a child.	no obligation in the past We didn't have to go to school on Saturdays.
must	changes to 'had to'	-
should have + pp / shouldn't have + pp	a past action which didn't happen: the advice / regret is too late You should have gone to bed earlier, now you have missed the train.	a past action which didn't happen: the advice / regret is too late You shouldn't have taken that job., it was a bad idea.

Past

Positive

Negative

had to / didn't have to

obligation in the past

I had to wear a school uniform when I was a child.

no obligation in the past

We didn't have to go to school on Saturdays.

must

changes to 'had to'

should have + pp / shouldn't have + pp

a past action which didn't happen: the advice / regret is too late

You should have gone to bed earlier, now you have missed the train.

a past action which didn't happen: the advice / regret is too late

You shouldn't have taken that job., it was a bad idea.

Remember 'must have done' is a modal verb of deduction or speculation, not obligation in the past. For example: Julie must have left. Her coat's not here.

Could have, should have, would have

These past modal verbs are all used hypothetically, to talk about things that didn't really happen in the past.

Could have + past participle

Could have + past participle means that something was possible in the past, or you had the ability to do something in the past, but that you didn't do it.

I could have stayed up late, but I decided to go to bed early.
They could have won the race, but they didn't try hard enough.
Julie could have bought the book, but she borrowed it from the library instead.
He could have studied harder, but he was too lazy and that's why he failed the exam.

Couldn't have + past participle means that something wasn't possible in the past, even if you had wanted to do it.

I couldn't have arrived any earlier. There was a terrible traffic jam (= it was impossible for me to have arrived any earlier).
He couldn't have passed the exam, even if he had studied harder. It's a really, really difficult exam.

We use could have + past participle when we want to make a guess about something that happened in the past. In this case, we don't know if what we're saying is true or not true. We're just talking about our opinion of what maybe happened.

Why is John late?

He could have got stuck in traffic.
He could have forgotten that we were meeting today.
He could have overslept.

We can also choose to use might have + past participle to mean the same thing:

He might have got stuck in traffic.
He might have forgotten that we were meeting today.
He might have overslept.

Should have + past participle

Should have + past participle can mean something that would have been a good idea, but that you didn't do it. It's like giving advice about the past when you say it to someone else, or regretting what you did or didn't do when you're talking about yourself.

Shouldn't have + past participle means that something wasn't a good idea, but you did it anyway.

I should have studied harder! (= I didn't study very hard and so I failed the exam. I'm sorry about this now.)
I should have gone to bed early (= I didn't go to bed early and now I'm tired).
I shouldn't have eaten so much cake! (= I did eat a lot of cake and now I don't feel good.)
You should have called me when you arrived (= you didn't call me and I was worried. I wish that you had called me).
John should have left early, then he wouldn't have missed the plane (= but he didn't leave early and so he did miss the plane).

We can also use should have + past participle to talk about something that, if everything is normal and okay, we think has already happened. But we're not certain that everything is fine, so we use 'should have' and not the present perfect or past simple. It's often used with 'by now'.

His plane should have arrived by now (= if everything is fine, the plane has arrived).
John should have finished work by now (= if everything is normal, John has finished work).

We can also use this to talk about something that would have happened if everything was fine, but hasn't happened.

Lucy should have arrived by now, but she hasn't.

Would have + past participle

Part of the third conditional.

If I had had enough money, I would have bought a car (but I didn't have enough money, so I didn't buy a car).

Because 'would' (and will) can also be used to show if you want to do something or not (volition), we can also use would have + past participle to talk about something you wanted to do but didn't. This is very similar to the third conditional, but we don't need an 'if clause'.

I would have gone to the party, but I was really busy. (= I wanted to go to the party, but I didn't because I was busy. If I hadn't been so busy, I would have gone to the party.)
I would have called you, but I didn't know your number. (= I wanted to call you but I didn't know your number, so I didn't call you.)
A: Nobody volunteered to help us with the fair. B: I would have helped you. I didn't know you needed help. (= If I had known that you needed help, I would have helped you.)

How to use 'Would'

We can use subject + would + infinitive (I would go) or subject + would + have + past participle (I would have gone).

'Would' has quite a lot of different uses. It's often a kind of past tense version of 'will'.

Remember that both 'had' and 'would' can be shorted to 'd. But only 'would' is followed by an infinitive without 'to'. 'Had' is followed by a past participle or by 'to + infinitive'.

The past of 'will' in reported speech

When we use 'will' in direct speech, we often use 'would' to change it into reported speech.

Direct speech: I will be there at 6pm.
Reported speech: She said that she would be there at 6pm.

Direct speech: We won't see you at the party.
Reported speech: They said that they wouldn't see us at the party.

Willingness in the past

In the present we use 'will' to talk about willingness (willingness means that you are happy to do something). For example, if we say 'I will help you', this means 'I'm offering to help you' or 'I'm happy to help you'. We use 'would' for the same meaning in the past. Usually, we use this in the negative (when we are not happy to do something) and we use 'won't' for the present and 'wouldn't for the past'.

His mother won't let him go to the party.
His mother wouldn't let him go to the party.

Habits in the past

When we were children, we would go to the beach every summer.
When I lived in Japan, I would take Japanese lessons three times a week.

This is similar in meaning to 'used to + infinitive'.

(We can also use 'will' for typical behaviour or habits in the present, though this is much less common than using 'would' for the past. An example in the present is 'she'll talk and talk for hours!')

Requests

We use both 'will' and 'would' to make requests. The meaning is the same for both, but a request with 'would' is more polite than a request with 'will'.

Will you please help me?
Would you please help me?

The second conditional

We use 'would + infinitive' in the second conditional.

If I had enough money, I would travel around the world.
If we lived in Madrid, we would study Spanish.

The third conditional

We use 'would + have + past participle' in the third conditional.

If I had gone to bed earlier, I wouldn't have been so tired.
If the train hadn't been late, we would have arrived on time.

With 'wish'

I wish that he wouldn't smoke so much.
I wish you would come to see me more often.

With set phrases to talk about what we want

We use 'would' with some set phrases. These have some 'willingness' meaning in them.

I would like some coffee.
She would rather go to the cinema.
We would prefer to leave immediately.
Would you mind helping me?