Auxiliaries and modals
Use helping verbs and modals to show ability, duty and possibility.
You have used verbs like is, has and does to build tenses. This lesson looks at these helping verbs and at modals, which add shades of meaning.
Auxiliaries are helping verbs that combine with a main verb; the primary ones are be, have and do, and modals such as can and must show ability, permission, duty or possibility.
Examples
- The baby is sleeping.
- Did you lock the door?
- Sita can play the sitar.
- May I come in?
- We should leave before dark.
How it works
Primary auxiliaries
Be forms continuous tenses and the passive, have forms perfect tenses, and do helps make questions and negatives.
He does not eat meat.
What modals express
Can and could show ability, may gives permission, must shows duty or certainty, should gives advice, and might shows a weak possibility.
You must show your ticket.
Modal grammar
A modal never adds -s, and it is followed by the bare infinitive.
She can speak Kannada.
Modals about the past
Use modal + have + past participle to talk about the past. Should have shows a missed duty, and must have shows a confident guess.
The road is wet; it must have rained.
Quick reference
| Modal | Main use | Example |
|---|---|---|
| can | present ability | Ali can swim. |
| could | past ability or polite request | Could you pass the salt? |
| may | permission or possibility | You may sit down. |
| might | weak possibility | It might snow tonight. |
| must | duty or strong deduction | He must be the new manager. |
| should | advice | You should rest. |
| would | polite offer or imagined result | Would you like some tea? |
Common mistakes
✕He cans run very fast.
✓He can run very fast.
A modal never takes -s.
✕She doesn't likes tea.
✓She doesn't like tea.
After does, the main verb stays in its base form.
✕You should have came earlier.
✓You should have come earlier.
After have, use the past participle come.
Worked example
Exercise 1
Tap the modal verb.
You should drink more water.
✓should
should is a modal giving advice.
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