Core Modals:
* Can (ability, permission, possibility)
* Could (ability, permission, possibility, polite request)
* May (permission, possibility)
* Might (possibility, uncertainty)
* Must (obligation, necessity)
* Shall (future tense, obligation, suggestion)
* Should (recommendation, obligation)
* Will (future tense, willingness, determination)
* Would (past tense of will, hypothetical situations, polite request)
Semi-Modals:
* Have to (obligation, necessity)
* Need to (necessity)
* Ought to (recommendation, obligation)
* Used to (past habit)
* Be going to (future intention)
* Be able to (ability)
* Be supposed to (obligation, expectation)
Note:
* Modal verbs are always followed by a base form of the verb.
* They are often used to express different shades of meaning, such as obligation, possibility, ability, or permission.
* Some modal verbs, like "shall" and "ought to," are not used as frequently in modern English.