Permission

can/may

You can/may park here.

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 (+also: needn’t + V1)

You don’t have to work at the weekend.

Prohibition

mustn’t/can’t

You mustn’t/can’t feed animals here.

Ability

can

I can sing.

I can’t paint well.

Advice

should (also: ought to)

You should study more.

Possibility

may/might/could

They might like your present.

Certainty

must/can’t

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