Permission

can/ may

You can/may park here.

Can we continue?

(Polite request – Could you repeat?)

Obligation

must/ have to

You must help my parents. (coming from inside – moral duty)

I have to come to work on time . (coming from outside)

No obligation

don’t have to

You don’t have to work at the weekend.

Prohibition

mustn’t/ can’t (+ V1)

You mustn’t/can’t feed animals here.

Ability

can

I can sing.

I can’t paint well.

past – could

Advice/ a good idea

should (+V1)/ shouldn’t

You should study more.

Possibility

may/might (more doubt)/could (+ V1)

She might like your present.

–

may not/might not

Certainty

+

must

–

can’t

She must be at home. She can’t be outside.