Modal verbs are ...
can / could / may / might/ must / shall / should / ought to / will / would
Modal verbs are used to express functions such as ability, advice, permission, obligation,possibility and prohibition.
must + infinitive
must = obligation
Examples must + infinitive
Dad must cut the gras. It's too long.
The pupils must learn vocabulary. They'll write a test.
She must go to the hospital. She's ill.
can - permission
Modal verbs - negative
Modal verbs and their substitutes
to be able to
English Modal verbs exercises
Modal verbs with free online exercises, examples and sentences, questions and negative sentences.
Online exercises English grammar and courses
Free tutorial Modal verbs. English Modal verbs exercises. English grammar easy to learn.