Modals of obligation

must / have to

don't have to

mustn't

should / shouldn't *

We use these modals to express a strong obligation

They are based on rules and what's "correct"

'have to' can be conjugated in any tense (past, present, future)

'must' only exists in the present, or with a future idea.

We use this verb to expres that it's not necessary to do something.

Basically, if you do it, it's because you decided to do it, even though nobody asked you to do it.

On Sundays, you don't have to pay for the entrance at the museums.

The meaning of this modal verb is an absolute prohibition.

According to the rules, you are not allowed to do something.

Do not confuse it with 'don't have to'

Other alternatives are:

can't / not be allowed to

These modals express a recommendation.

In the end, you have the final decision.

You shouldn't eat junk food all the time.

We should practice speaking English at home.