Modal verbs

Modal verbs, sometimes called modals, are auxiliary verbs (helping verbs). They express such things as possibility, probability, permission and obligation.

• Can, could, might, may, must, should, will, would and shall are modal verbs.
• We use a modal verb before a second verb.
• Modal verbs are not followed by ‘to’.
• Modal verbs can have more than one meaning and usage.

Modal verbs to express ability

• Can, could, was able to – modal verbs to express ability
  

Modal verbs to express permission

• Can, can’t, could, may: modal verbs for permission

Modal verbs to express probability and certainty (modal verbs of deduction)

• Present tense modal verbs of deduction: must, can’t, may, might, could
• Past tense modal verbs of deduction: must have, can’t have, couldn’t have

Modal verbs to express obligation

• Should – to express weak obligation, advice
• Should have – to express unfulfilled obligation in the past

Modal verbs – past tense forms and negatives

• Modal verbs – past tense forms
• Modal verbs – negative forms
• ‘Had to’ vs. ‘must have’