Models – Can and Could, May and Might, Must and Have to

MODALS – CAN and COULD

1. Use of “Can”

Can is used for:

  • Present ability (what someone is able to do now)
  • Permission (asking or giving permission)
  • Possibility (something that might happen)

Structure: Subject + can + base verb

Examples: She can swim. (ability). Can I use your pen? (permission). It can be dangerous. (possibility)

2. Use of “Could”

Could is used for:

  • Past ability (what someone was able to do earlier)
  • Polite permission or request
  • Weak/less certain possibility

Structure: Subject + could + base verb

Examples:She could swim when she was young. (past ability). Could I come in, please? (polite permission/request). It could rain today. (weak possibility)

3. Difference Between “Can” and “Could”

  • Can = present ability, direct permission
  • Could = past ability, polite request, weaker possibility

Examples: She can drive now. (present ability). She could drive when she was 18. (past ability)

  • Can I come in? (direct)
  • Could I come in? (polite)

4. Negative Forms

  • can not / cannot → cannot
  • could not → couldn’t

Examples:She cannot drive. He couldn’t understand the question.

5. Interrogative (Question) Forms

  • Can + subject + base verb?
  • Could + subject + base verb?

Examples:Can you help me ? Could you explain this ?

6. Important Rule

  • After can or could, always use the base form of the verb. (V1)
  • Correct: can go / could go
  • wrong: can goes / could went

Quick Usage Reminder: can → present, could → past / polite / less sure

MODALS – MAY and MIGHT

1. Use of “May”

May is used to show: Permission (formal), Possibility (stronger chance), Formal requests

Structure: Subject + may + base verb

Ex: May I come in? (permission), She may join us later. (possibility), May I leave early? (formal request)

2. Use of “Might”

Might is used to show: Weak possibility, Doubt or uncertainty, Less sure than may

Structure: Subject + might + base verb

Ex: It might rain today. (weak possibility), She might be late. (uncertainty)

3. Difference Between “May” and “Might”

  • May = stronger possibility, more sure, more formal.
  • Might = weaker possibility, less sure, uncertain.

Ex: She may come. (there is a good chance), She might come. (not sure / less chance)

4. Negative Forms

  • may not
  • might not

Ex: He may not agree. She might not come today.

5. Interrogative (Question) Forms

  • May + subject + base verb?
  • Might + subject + base verb? (rare in daily use)

Ex: May I leave early ? Might I ask a question ? (rare/polite/formal)

6. Rule: After may and might, always use the base form (V1) of the verb.

Correct: may go / might go

wrong:  may goes / might went (wrong)

Memory Line: May → strong possibility, Might → weak possibility

MODALS – Must and Have to

1. Use of “Must”

  • Shows strong obligation, duty, or necessity.
  • The obligation comes from the speaker’s personal feeling, decision, or authority.

Structure: Subject + must + base verb

Ex: You must follow the rules. (strong obligation), She must study hard. (necessity felt by the speaker)

2. Use of “Have to”

  • Shows obligation or compulsion because of rules, laws, or situations.
  • The obligation comes from outside, not from the speaker.

Structure: Subject + have to / has to + base verb

  • have to → I, you, we, they
  • has to → he, she, it, singular name

Ex: I have to wake up early. (situation/routine), He has to wear a uniform. (rule)

3. Difference Between “Must” and “Have to”

  • Must = personal obligation (speaker decides)
  • Have to = outside obligation (rule/law/situation decides)

Ex: You must finish this today. (speaker’s authority), You have to finish this today. (external rule)

4. Negative Forms

  • must not (mustn’t) → prohibition / not allowed
  • do not have to (don’t have to) → no need / not necessary

Ex: You must not smoke here. (prohibited), You do not have to come tomorrow. (not necessary)

5. Interrogative (Question) Forms

  • Must + subject + base verb?
  • Do/Does + subject + have to + base verb?

Ex: Must I attend the meeting?, Do you have to wear a uniform?

6. Key Memory Tips

  • Must → Speaker control / Personal decision / Strong duty
  • Have to → Rule control / Law or situation decides

Speaker Control = Must

Rule Control = Have to