Modal verbs

MODAL VERBS

• Ability and permission: can, could, be able to, be allowed to
• Possibility and deduction: may, might, can, could, must (certainty), can't
• Obligation and necessity: must, have to, need, 
• Giving advice: should, ought to
• Lack of obligation: don’t have to,  needn’t to
• Prohibition: mustn’t

PERFECT MODALS

• Advisability: asking for & giving advice about an action that has already occurred. (it may create a sense of regret or blame)

             - SHOULD/OUGHT TO + HAVE + PAST PARTICIPLE
             - MIGHT/COULD + HAVE + PAST PARTICIPLE

• Degrees of certainty: making assumptions or conclusions about PAST actions or situations.

             - MUST + HAVE + PAST PARTICIPLE ( logical conclusion/deduction, certain 95%)
             - COULD/HAVE/MIGHT + HAVE + PAST PARTICIPLE (not certain - 50%)
             - COULDN'T + HAVE + PAST PARTICIPLE (impossibility)

Practice

• Modal verbs I
• Modal verbs II
• Lots of  different exercises
•  Modal verbs 1 2 3 4 5 6 7
•  Modal perfects 1 2