One small verb. A big change in meaning.
Modal verbs express ability, permission, obligation, advice, possibility, and certainty. They usually come before the main verb and change the speaker's attitude to an action.
THE FORMULA
Subject + modal + base verb
She can solve the problem.
Not: She cans to solve the problem.
QUESTIONS & NEGATIVES
Modal + subject + verb?
Could you explain the situation?
Subject + modal + not + verb
They shouldn't ignore the warning.
Remember: no -s after he/she/it, no to after central modals, and no do/does in questions with can, could, must, should, may, might or would. Have to behaves differently: she has to leave; does she have to leave?
CHECKPOINT 01 · Build the sentence
Choose the grammatically correct option.
CAN vs COULD
CAN — now
Use can for present ability, available options, and informal permission.
Even though the instructions are complicated, Maya can assemble the desk without help.
Can we reschedule the meeting for Friday?
COULD — past / polite / possible
Use could for general past ability, polite requests, suggestions, and uncertain possibilities.
When my grandfather was younger, he could repair almost any engine.
Could you explain why the results changed?
Important distinction: For one particular successful event in the past, managed to or was/were able to is often more natural than affirmative could: “After three attempts, we managed to unlock the door.”
CHECKPOINT 02 · Choose the meaning
MUST vs HAVE TO
Both express necessity. Must often highlights the speaker's strong feeling or an instruction; have to often describes requirements imposed by circumstances. This is a tendency, not an absolute rule.
MUST
I must apologise for the way I reacted yesterday.
The speaker feels a strong personal need to apologise.
HAVE TO
Because the train leaves at six, we have to leave the house before five.
The schedule creates the necessity.
For past obligations, use had to: “We had to cancel the trip because the airport was closed.” For questions: “Does your brother have to work on weekends?”
CHECKPOINT 03 · Rules and obligations
MUSTN'T ≠ DON'T HAVE TO
MUSTN'T = FORBIDDEN
You mustn't share your account password with strangers.
The action is prohibited.
DON'T HAVE TO = OPTIONAL
You don't have to print the tickets because the digital versions are accepted.
The action is not necessary.
Compare: “You mustn't tell anyone” means keep it secret. “You don't have to tell anyone” means sharing the information is optional.
CHECKPOINT 04 · Forbidden or optional?
SHOULD / SHOULDN'T
Use should to recommend a sensible action, and shouldn't to advise against an action. A recommendation is weaker than a strict requirement.
GOOD ADVICE
You should back up your files before updating the operating system.
ADVICE AGAINST
You shouldn't make an important decision while you're extremely upset.
To ask for advice, put should before the subject: “Should I tell my friend what actually happened?”
CHECKPOINT 05 · Give sensible advice
MAY / MIGHT / COULD
Use these verbs when something is possible but not certain. Might can sound more tentative, but there is no fixed percentage difference between may and might.
UNCERTAIN FUTURE
Depending on the weather, we might postpone the outdoor concert.
UNCERTAIN PRESENT
Leo may be working late; he hasn't replied to any messages.
May I ...? is also used to ask for formal permission: “May I ask a question before the presentation begins?”
CHECKPOINT 06 · Possibility or certainty?
WOULD
Would is common in polite requests, invitations, preferences, and imaginary situations.
POLITE REQUEST
Would you mind explaining how you reached that conclusion?
Would you mind + verb-ing
IMAGINARY RESULT
If I had the opportunity to study abroad, I would choose a university with an international programme.
Would like + to + verb: “I'd like to improve my public-speaking skills.” Unlike can and must, the phrase would like is followed by to before another verb.
CHECKPOINT 07 · Be polite and precise
MUST / MIGHT / CAN'T
Modals also help us draw conclusions from evidence, not just talk about rules.
MUST = STRONG CONCLUSION
Her coat is still here, so she must be somewhere in the building.
MIGHT = POSSIBLE
The package might be at reception, but nobody has checked yet.
CAN'T = IMPOSSIBLE BASED ON EVIDENCE
He can't be in Paris right now — I just saw him in the library.
PAST DEDUCTION
She must have forgotten the appointment. Nobody answered the door.
modal + have + past participle
CHECKPOINT 08 · Read the evidence
REAL-LIFE DECISIONS
Read each situation carefully. Choose the modal that best matches the intended meaning.
FINAL CHECKPOINT · Mixed modal verbs
YOUR TURN TO SPEAK.
Give detailed answers. Explain your reasons and use at least two different modal verbs in each response.
Which school rules should students follow? Which rules might be unnecessary? Why?
Your best friend wants to quit a hobby they used to love. What advice would you give?
Your flight has been cancelled and your phone battery is almost empty. What could you do? What must you do first?
What should teenagers know about protecting personal information? What mustn't they share?
What might change in education over the next twenty years? What skills will students have to develop?
Writing challenge
Write 100–140 words: “Five rules I would change in my school — and five I would keep.” Use must, mustn't, have to, don't have to, should, might and would. Explain each choice.
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