must

(modal auxiliary, defective) To do with certainty; indicates that the speaker is certain that the subject will have executed the predicate.

(modal auxiliary, defective) To do as a requirement; indicates that the sentence subject is required as an imperative or directive to execute the sentence predicate, with failure to do so resulting in a failure or negative consequence.

(modal auxiliary, defective) Used to indicate that something that is very likely, probable, or certain to be true.