Modal Verbs
Master modal verbs in English. Learn to express ability, possibility, obligation, permission, and advice with can, could, must, should, may, and might.
What Are Modal Verbs?
Modal verbs are auxiliary verbs that express attitude, possibility, obligation, permission, ability, or advice. They have no infinitive, gerund, or past participle forms, and they are used with the main verb in the bare infinitive (without to).
📋 Quick Reference
Basic Modal Verbs
The main modal verbs and their most common uses.
| Modal | Main Use | Example | Meaning |
|---|---|---|---|
| can | ability, permission | I can swim | I can swim |
| could | past ability, possibility | I could help you | I could help you |
| may | formal permission, possibility | May I go? | May I go? |
| might | weak possibility | It might rain | It might rain |
| must | strong obligation | You must study | You must study |
| should | advice, weak obligation | You should rest | You should rest |
| will | future, willingness | I will help you | I will help you |
| would | conditional, politeness | I would like coffee | I would like coffee |
Puedo hablar inglés
I can speak English
I can speak English
Debes hacer tu tarea
You must do your homework
You must do your homework
¿Puedo usar tu teléfono?
May I use your phone?
May I use your phone?
Basic Rules
All modal verbs follow these rules:
- They are followed by the bare infinitive (without 'to')
- They do not take -s in the third person
- They do not use do/does/did in negatives and questions
- They come before the main verb
Ability
To express physical or mental ability, capacity, or possibility.
| Modal | Tense | Use | Example |
|---|---|---|---|
| can | present | current ability | I can drive |
| could | past | past ability | I could swim when I was 5 |
| be able to | all tenses | specific ability | I was able to finish the project |
| cannot/can't | present | lack of ability | I can't speak French |
Puedo tocar el piano
I can play the piano
I can play the piano
Cuando era niño, podía correr muy rápido
When I was a child, I could run very fast
When I was a child, I could run very fast
No pude terminar el trabajo a tiempo
I wasn't able to finish the work on time
I wasn't able to finish the work on time
Permission
To ask for, give, or deny permission in formal or informal situations.
| Modal | Formality | Use | Example |
|---|---|---|---|
| can | informal | everyday permission | Can I go to the bathroom? |
| may | formal | formal permission | May I leave early? |
| could | polite | asking politely | Could I borrow your pen? |
| cannot/can't | informal | denying permission | You can't smoke here |
| may not | formal | formal denial | You may not enter |
¿Puedo salir temprano?
May I leave early?
May I leave early?
¿Podrías prestarme tu libro?
Could you lend me your book?
Could you lend me your book?
No puedes usar tu teléfono aquí
You cannot use your phone here
You cannot use your phone here
Levels of Formality
Order of formality when asking for permission:
- Most formal: May I...?
- Polite: Could I...?
- Informal: Can I...?
- Choose according to context
Possibility
To express different degrees of possibility or probability.
| Modal | Degree | Use | Example |
|---|---|---|---|
| must | very high (90%) | logical deduction | You must be tired |
| may | medium (50%) | real possibility | It may rain tomorrow |
| might | low (30%) | weak possibility | I might come to the party |
| could | possible | theoretical possibility | It could be true |
| can't | impossible | impossibility | That can't be right |
Debe estar cansado (muy probable)
He must be tired
He must be tired (very likely)
Puede que llueva mañana
It may rain tomorrow
It may rain tomorrow
Podría venir a la fiesta
I might come to the party
I might come to the party
Degrees of Possibility
Order of probability (from highest to lowest):
- must (almost certain)
- may (possible)
- might (less likely)
- could (theoretically possible)
Obligation
To express different types and degrees of obligation.
| Modal | Type | Degree | Example |
|---|---|---|---|
| must | personal obligation | strong | I must finish this today |
| have to | external obligation | strong | I have to work tomorrow |
| should | advice/recommendation | weak | You should exercise more |
| ought to | moral advice | weak | You ought to apologize |
| don't have to | no obligation | none | You don't have to come |
| mustn't | prohibition | strong | You mustn't smoke here |
Debo terminar este trabajo hoy
I must finish this work today
I must finish this work today
Tengo que trabajar mañana
I have to work tomorrow
I have to work tomorrow
Deberías hacer más ejercicio
You should exercise more
You should exercise more
Must vs Have to
Important differences:
- Must: personal, internal obligation
- Have to: external obligation, rules
- Must: more subjective
- Have to: more objective
Advice
To give advice, suggestions, and recommendations.
| Modal | Strength | Use | Example |
|---|---|---|---|
| should | recommendation | general advice | You should see a doctor |
| ought to | moral | moral advice | You ought to help them |
| had better | urgent | strong advice | You'd better hurry |
| could | suggestion | soft option | You could try yoga |
| might want to | suggestion | very soft option | You might want to call her |
Deberías ver a un doctor
You should see a doctor
You should see a doctor
Deberías ayudarlos
You ought to help them
You ought to help them
Mejor te apuras
You'd better hurry
You'd better hurry
Common Mistakes
Correct: Bare infinitive without to ✅
I can to swim. → I can swim.
Correct: Modals do not change ✅
He cans swim. → He can swim.
Correct: Add not directly ✅
I don't can swim. → I can't swim.
Correct: Understand the difference ✅
I must work (personal) vs I have to work (external rule)
Correct: Use can in informal contexts ✅
May I go? (formal) vs Can I go? (informal)
Important Rules
1. Basic structure
Modal verbs follow a specific structure.
- Subject + modal + bare infinitive (without 'to')
- They do not change according to the person
- They do not use auxiliaries do/does/did
- The negative is formed with 'not'
2. No tense forms
Modals do not have past, present, or future forms.
- Use 'could' for the past of 'can'
- Use 'would' for the past of 'will'
- For other tenses, use 'be able to'
- Or use periphrastic verb forms
3. Context and formality
Choose the modal according to context.
- Formal: may, ought to
- Informal: can, should
- Polite: could, might
- Consider the situation