Modal Verbs

Can / Could  We use "can" and its past form "could" to express ability.

Can Interactive book

May / Might We use these modal verbs to express that something is likely to happen.

We can also use can, could, may and might for permission and requests

Must and mustn't  Interactive book. We use "must" to express rules, obligation or necessity. We use "mustn't" to express prohibition.

Have to We use this modal verb to express obligation and necessity.

Should or shouldn't?  We use "should" to give advice or express that something is a good idea.