Using Modals

Ability

We use can, could and be able to when speaking about ability (or lack of ability).

Example;

I can eat a full pizza by myself.

Nana could walk by the time she was two.

You should be able to hear the horn from your room.

In each case, we use the modal (can/ could/ be able to) before the base form of the main verb.

Permission

We use can, could or may when asking for or giving permission. We use ‘may’ when in a more formal situation (for example when asking permission from your teacher).

Example; Can I sleep over at Mandy’s?

Or

Could I sleep over at Mandy’s?

Example; May I use the bathroom?

Or

May I be excused?

Necessity

We use must, have to, need to, don’t have to, needn’t when speaking about something that is necessary. (NB: don’t = do not and needn’t = need not)

Example; They need to work faster if they want to meet the deadline.

You don’t have to submit your work when the bell rings.

You must join a sports team if you want to be a school prefect.

Probability

We use can, could, may or might when speaking about the likelihood that something will happen or not happen.

Example; We could watch a movie tonight.

It might rain today.

You may miss your break if you do not work faster.

Obligation

We use must, have to, and should to show obligation.

To show strong obligation, use have to or must

Example; You have to watch your sister’s performance.

You must watch your sister’s performance.

To show mild obligation, use should

Example; You should watch your sister’s performance.