Modal Verbs

Among all the aspects of grammar modal verbs seem to be the easiest to teach. All you need to do is make sure your students understand there is a group of verbs which act differently from other verbs.

They are used to give the sentence extra meaning. Structurally, they are also much easier than other grammatical points: they have the same form for all the pronouns, they form questions by means of inversion and negations by means of NOT (with a few exceptions which we mention below).

To start with, let’s introduce some of the most important modal verbs:

CAN – is used to describe the ability to do something eg: I can swim. / I can’t do my homework.

It is also used to make a polite request.

eg: Can I have a glass of wine?

COULD – We use could to describe a past ability to do something (could is the past of can), eg When I was young, I could play computer games for hours.

It is also used to make a very polite request.

eg: Could I have a glass of wine?

BE ABLE TO – like ‘can’, means to have the ability to do something. Sadly, ‘CAN’ can’t be used in the future (we can’t say I will can) so we use ‘ABLE TO’ (I will be able to)

Note that here the form changes depending on the pronoun – it’s different for I, you, he etc. (the verb ‘be’, which is part of the expression, changes)

eg: I am able to do it. / You are able to swim. / She is able to speak German.

MUST – we use this when we are obliged or required to do something. It is a very strong word that normally means there should be no other choice or option, eg You must obey the law.

Make sure you explain to your students that we do not create the negative of MUST by means of adding NOT. If we want to negate a sentence with MUST, we have to change MUST to HAVE TO and negate that structure.

eg I must see him tomorrow. → I don’t have to see him tomorrow.

I must do this research. → I don’t have to do this research.

The negative, MUSTN’T, has a completely different meaning and is used when we are not allowed to do something. 

eg: You mustn’t drink and drive.

You mustn’t smoke in here.

HAVE TO – is pretty much the same as ‘must’ but not quite as strong, see the following example: 

You must drink water or you will die. 

You have to clean your room.

SHOULD – We express moral obligation or the right thing to do by means of ‘should’. It’s not as strong as ‘must’, eg

I should stop smoking. 

You should tell him the truth.

We also use ‘should’ when we want to suggest something. 

eg: You should stop smoking.

MAY MIGHT – When we want to suggest that something is possible or we haven’t decided yet, we can use MIGHT or MAY.

eg: I might / may go to the pub tonight.

It may / might be raining later.

NEED – expresses a requirement or urgent want, something that has become necessary. 

eg: We need to stop for petrol.

I need to see him!


There are other modal verbs, such as: Ought to, Shall, Will, Would, Had better and Used to. They are either less important (because they are not used as often) or they are explained on their own or as part of a different grammar point.