Modal verbs
Using modals for ability, permission, obligation, advice and deduction in the present and the past.
Modal verbs (can, could, must, should, may, might and others) add meaning such as ability, permission, obligation, advice and deduction to a main verb. They are followed by the bare infinitive (must go, should leave) and do not change with the subject. The biggest difference for advanced learners is meaning: 'mustn't' means it is forbidden, while 'don't have to' means it is not necessary; 'must be' is a confident present guess, while 'must have been' is a confident guess about the past. To talk about the past we use 'modal + have + past participle', for example: 'You should have told me earlier' (a regret) or 'She can't have left, her coat is still here' (a deduction). For example: 'He isn't answering his phone, so he must be sleeping.'
Rules
- 1Modals are followed by the bare infinitive and never take an -s, -ed or -ing ending: 'She must go' (not 'must to go').
- 2For obligation use 'must' / 'have to'; 'mustn't' = it is forbidden, but 'don't have to' = it is not necessary (no obligation).
- 3For advice use 'should' / 'ought to'; 'had better' gives strong advice or warning about the near future ('You'd better hurry').
- 4For present deduction use 'must' (sure it's true), 'can't' (sure it's false) and 'might / may / could' (possible).
- 5For the past use 'modal + have + past participle': deduction (must / can't / might have done) and regret or criticism (should have done).
Practice
10 easy · 10 medium · 10 hard