Modals
Modals are helping verbs that show ability, possibility, permission, duty, necessity or deduction. They take the base form of the verb (no to, no -s, no -ing). Exceptions: ought to, have to, used to.
| Modal | Use | Example |
|---|---|---|
| can / could | ability (present / past); polite request | She can swim. He could run fast. Could you help me? |
| may / might | possibility (might = weaker); formal permission; wish; purpose | It may rain. May I come in? May you live long! … so that he may pass. |
| must | strong obligation; logical certainty | We must obey the law. She must be tired. |
| mustn't | prohibition | You mustn't smoke here. |
| needn't / don't have to | no necessity | You needn't bring an umbrella. |
| can't | logical impossibility | He can't be at home. |
| should / ought to | duty, advice | You should obey. You ought to respect elders. |
| shall | offer/suggestion with I/we | Shall I open the window? Shall we go? |
| will / would | future, promise; polite request; conditional; reported will | Would you lend me…? If I were you, I would… |
| had better | strong advice | You had better leave now. |
| would rather … than | preference | I would rather die than beg. |
| used to | past habit | He used to walk to school. |
| dare / need | as modals in negatives/questions + base verb | How dare he insult me? You need not go. (But: You do not need to go.) |
Modal + have + V3 (about the past)
- must have gone = certain it happened.
- can't have seen = impossible it happened.
- may/might have missed = possibly happened.
- should have told = it was right, but not done.
- could have helped = was possible, but not done.
- needn't have bought = done, but was unnecessary.
lest … should (no not): Walk fast lest you should miss the bus.