Modal Verbs to Express Obligation, Permission and Necessity

Modal Verbs:

Verbs used with other verbs to express obligation, permission, prohibition or necessity (among others): should, can, must, ought to, may
Verbs used as modal verbs but are not strict modal verbs: have to, need to

 

Explanation and exercises:

https://test-english.com/explanation/b2/modal-verbs-permission-obligation-prohibition-necessity/ 

https://learnenglish.britishcouncil.org/grammar/b1-b2-grammar/modals-permission-and-obligation

https://www.lewolang.com/english-grammar/31/modal-verbs-of-obligation