An article by Kerry Maxwell and Lindsay Clandfield on ways to approach teaching modal verbs.


  • Student: Can I go to the bathroom, sir?
  • Teacher: I’m sure you can, but you may not.

This old joke plays on different interpretations of can. The student is asking for permission, whereas the teacher is talking about ability. Some people might say that the student’s use of can is incorrect (i.e. the student should say May I go to the bathroom?). This view, however, is based on a very narrow understanding of modality and modal verbs in English.

in this article we take a closer look at modal verbs. We begin by looking at their function in English and exploring basic properties. We then go on to look in more detail at the most common uses of the important modal verbs can, could, will and would. In article Modal verbs 2, we complete the story by covering may, might, must, should and ought to.

As well as making simple statements or asking questions, we may sometimes want to express our intentions and attitudes, talk about necessity and possibility, or make offers, requests, or suggestions. In English, these uses of language are usually expressed by a set of verbs called modals. Modals always occur with other verbs, and can be thought of as a special kind of auxiliary verb, e.g.

I must go to the post office.

Can I borrow your umbrella?

The most commonly used modals in English are:

can / could / will / would / may / might / must / ought to / should

Modals are mainly used when we want to indicate our attitude to what we are saying, or when we are considering how what we say will affect the person we are communicating with. Compare:

She’s the oldest. vs. She might be the oldest.

(Here the modal shows that the speaker is not absolutely sure that the statement is true.)

Close the door. vs. Could/would/will you close the door?

(Here the modals turn an instruction into a polite request.)

a) Modals are always followed by the base form of the verb, e.g.

I might play tennis tomorrow.

You ought to tell her.

Sometimes a modal is followed by the base form of auxiliaries have or be, followed by a participle, e.g.

I might be playing tennis tomorrow.

You ought to have told her.

In passive structures, a modal is followed by be or have been and a past participle, e.g.

She ought to be disqualified.

The door might have been locked.

b) Modals never inflect, i.e. they have no –ing or –ed forms, and do not take –s in the third person singular present.

Note: the modal form could is sometimes thought of as the past tense of can when it refers to the ability to do something, e.g.

Louise can read. = Louise could read when she was three.

and also in reported speech, when the modal form would is also thought of as the past tense of will:

'Jackie can come.' = She said that Jackie could come.

'You will be late.' = I told her that she would be late.

c) Unlike other verbs, modals do not use do and did to form negatives. Negatives are formed by putting not immediately after the modal, except in the case of ought to, where the negative form is ought not to (which is sometimes abbreviated to oughtn’t to). The negative of can is written as one word cannot, more usually shortened to can’t. Shall not and will not are abbreviated to shan’t and won’t respectively. Could not and would not usually appear as couldn’t and wouldn’t, e.g.

I might not play tennis tomorrow.

You ought not to tell her.

She can’t come.

We won’t be ready until five.

d) Modals do not use do and did to form questions. Questions are formed by placing the modal before the subject. In the case of ought to, ought is placed before the subject and to after it, e.g.

Can she speak Spanish?

Ought you to tell her?

Wouldn’t he help you?

When will and would are used after a pronoun, they are often shortened to the contracted forms 'll and ’d and joined to the pronoun, e.g.

I’ll help if you want.

I’m sure she’ll agree.

It’d be better if you told her yourself.

He said that he’d walk home.

Modal verbs can and could are used to show that someone has the ability to do something. Can is used for the present, and could is used for the past, e.g.

Tom can play chess.

I can’t pick the box up, it’s too heavy.

Louise could read when she was three.

I stood on a chair, but I still couldn’t see.

Can and could: permission

Can and could are also used to express the idea of giving or asking for permission to do something, e.g.

You can use my phone if you want.
I’m sorry but you can’t bring drinks in here.
Can I borrow your pen, please?
Could Tom sit next to you?

Sometimes can and could are used to talk generally about permission, rather than giving it or asking for it. In this sense, can is used for the present and could is used for the past, e.g.

There’s a sign saying that you can’t park in front of the station.

I can stay up until nine. Mum said so.

We couldn’t keep pets when we lived in the flat.

There was a time when you could park your car anywhere.

Can and could: possibility

a) Can and could are often used to suggest possible future actions.

You can/could go on the train if you prefer.

Note: can expresses a more definite possibility than could, eg:

If you don’t like it, I can paint it a different colour. vs If you don’t like it, I could paint it a different colour.

b) Could is often used to say that something is or was possibly true, e.g.

He could be working late tonight.

It could be difficult to get there in time.

She could have missed the last bus.

c) Can is sometimes used to say that something is generally possible:

Smoking can seriously damage your health.

Paris can be very hot in summer.

In this sense, can often has the meaning ‘sometimes’, e.g.

Owning a dog can be expensive. (= Owning a dog is sometimes expensive.)

d) Can’t and couldn’t are sometimes used to show that something is or was impossible, e.g.

This can’t be Sam’s coat, it’s far too big.

You couldn’t have seen Simon yesterday, he’s in America.

Will and would: requests

Will and would are often used when making requests, e.g.

Will you give me a lift?

Would you pass me the salt?

Note that would is less direct and sounds more polite than will.

Will and would: intentions

Will is often used to state an intention to do something, e.g.

I’ll talk to you later.

We’ll call you when we’re ready.

I won’t ask for any money.

We won’t leave without you.

It can also be used to talk about someone’s willingness to do something, e.g.

Ask Sarah if she’ll take them.

I’ve asked her, but she won’t come.

Wouldn’t can be used to show that someone was unwilling to do something in the past, e.g.

I asked her, but she wouldn’t come.

Will and would: habits

Will and would are sometimes used to describe habits or characteristic behaviour. Will is used for habits or behaviour in the present and would is used for habits or behaviour in the past, e.g.

Every day she’ll come home and immediately turn on the TV.

John is so kind. He’ll always give me a lift if I ask him.

He’d always turn and wave at the end of the street.

In those days people would grow all their own vegetables.

When speaking, will and would in this sense are often stressed in order to criticize someone’s usual behaviour, e.g.

She will keep talking when I’m trying to concentrate.

He just wouldn’t tidy his room when I asked him.

Will and would: certainty

Will can be used to say that something is certainly true, e.g.

There’s someone coming to the door. – Oh, that’ll be the window cleaner.

Louise will be at home by now.

Matthew won’t want to be disturbed if he’s working.

In this sense, will is often followed by be + -ing to talk about what is certainly happening, or have + past participle to talk about what has certainly happened, e.g.

Louise will have arrived by now.

He won’t have tidied the house, he never does.

I expect Matthew will be working in the study.

Kelly won’t be helping, I’m sure of that.

Will and would: unreal situations

Whereas will is often used to make predictions about a real event in the future, e.g.

We’re going to have a few days holiday in Scotland. – Oh, that’ll be nice.

would is often used to make a prediction about an unreal event, i.e. an event which may or may not happen, e.g.

We’re thinking of having a few days holiday in Scotland. – Oh, that would be nice.

In this sense, would often occurs in a sentence with if to talk about what might happen if something else happens, e.g.

What would you do if you lost your job?

Would also often occurs with verbs such as like, love, etc, to talk about what someone wants to do, e.g.

I would like to know more.

We’d love to have twins.

She’d prefer to go to Scotland.

Would have + past participle is used to talk about an unreal situation in the past, i.e. a situation that might have happened, but didn’t, e.g.

Pete would have helped if he hadn’t been unwell.

What would you have done if you’d lost your job?

It similarly occurs with verbs such as like, love, etc to show what someone wanted to do, but didn’t:

We went to Wales, but Jack would have preferred to go to Scotland.