Learn English > Grammar > Verbs > Modals > have to, must have to, must Have to is NOT an auxiliary verb (it uses the verb have as a main verb). We include have to here for convenience. Must is a modal auxiliary verb. In this lesson we look at have to, must and must not, followed by a quiz to check your understanding. have to for objective obligation We often use have to to say that something ...

We use have to / must / should + infinitive to talk about obligation, things that are necessary to do, or to give advice about things that are a good idea to do.

"Must" is a modal verb most commonly used to express certainty. It can also be used to express necessity or strong recommendation, although native speakers prefer the more flexible form "have to."

(used to express that logically there is a need for the action or state of the next verb to be true): There must be some mistake (= there cannot be any other explanation possible). She must have had a very good reason for what she did.

The meaning of MUST is be commanded or requested to. How to use must in a sentence.

MUST definition: to be obliged or bound to by an imperative requirement. See examples of must used in a sentence.

A must is something that's so important it can't be missed or ignored. When you're taking kayaking lessons, a lifejacket is a must.