1Foundations — the nutshell A2

The function of a modal is to add opinion or colour to a phrase — how possible, how obligatory, how polite, how certain.

The nine pure modals at a glance

The two iron rules

Insight: every modal carries a future

The meaning map — pick the function, get the modals

2Strength meter B1

Modals don’t just have meanings — they have force. Click a step on each meter to feel how the modal sits on the strength dial. Same idea, very different conviction.

3Can / could / be able to A2

The ability/possibility trio. Can only has two real forms (present can, past could) — that’s why be able to exists: it carries the missing tenses.

CAN — three jobs

Ability / inability

• The teacher can help us learn English.
• I can’t leave here now.
• He can’t fly that plane! (no skill)

Possibility / impossibility

• I can visit you next week.
• He cannot appear in court under these circumstances.
• I can buy that car next month.

Requests A2

• Can you give me the book? (neutral, friendly)
• Can you please open that window? (direct)
• Could you please open that window? (polite, respectful)
• I was wondering if you could tell me where…? (very polite, formal)

COULD wears four hats B1

Why can needs be able to

Can has only two forms (can / could). Whenever you need a different tense — perfect, future, infinitive, -ing — switch to the relay-runner be able to.

Was/were able to vs managed to B2

Use could for general past ability. For a specific success in a difficult moment, switch to was/were able to or managed to.

4May, might (and could) B1

The possibility trio. May and might are near-synonyms; could joins them for the same job. The big traps are may not vs couldn’t, and maybe vs may be.

The basic move — “perhaps”

• It may rain later. = Perhaps it will rain.
• She might know the answer.
• Where’s Ben? Ask Kate — she might know.
• It’s a strange story, but it could be true.
• The story could be true, but I don’t think it is. (not “can be true”)

Are may and might identical?

MAY for formal permission B1

• May I come in? (very polite, formal)
• You may leave the room when you have finished. (written instruction)
• Visitors may not enter without a pass. (formal prohibition)

maybe vs may be A2

Real-life uses

• You’re looking for Ben. He might be in his office. He may be having lunch. (brainstorming possibilities)
• I can’t find Max. May I come back later? (permission)
• Take an umbrella — it might rain later.
• I haven’t decided yet. I might come to the party, I might not.
• He could be in the canteen — I’d start there.

5Will, would, shall B1

The future-and-hypothetical family. Will is your default future and prediction word; would is its hypothetical twin; shall is the polite first-person ghost.

WILL — the four jobs

WOULD — four hats too

SHALL — suggestion (only with I / We) B1

• Shall we start? (I suggest we start)
• Shall we go out for lunch?
• Shall I open the window? (= Should I open the window?)
• I’ve got no money. What shall I do? (asking for a suggestion)

In affirmative statements, I shall call you later sounds old-fashioned in modern English; we use I will call you later. Shall survives in legal/formal writing (“the tenant shall pay…”) and in shall I / shall we questions.

Quick comparison

6Must, have to, need to A2

The obligation family. Must = personal / strong; have to = external / fact; need to = neutral necessity. The trickiest move is mustn’t vs don’t have to — they’re opposites of different things.

MUST vs HAVE TO — who’s putting the pressure on?

In positive statements, must and have to are often interchangeable in casual speech. The textbook split is internal vs external obligation; in real life, the difference is small unless you want to emphasise where the pressure comes from.

The four corners — positive, negative, obligatory, optional

Past obligation — had to (not musted) A2

Must has no past form. For past obligations, switch to had to.

• I had to leave early yesterday. (not “I must have leave”)
• He had to appear in court several times.
• Last week Tina broke her arm and had to go to hospital.

NEED TO — the neutral cousin B1

• You need to sign here.
• I don’t need to finish it tonight — tomorrow is fine. (= don’t have to)
• You needn’t worry. (formal-ish; same as “don’t need to worry”)
• I didn’t need to wait long — she arrived almost immediately. (no obligation; she came fast)
• I needn’t have rushed. (I rushed but it was unnecessary — modal perfect)

MUST for deduction (NOT obligation) B2

Same word, very different job — “logical certainty” rather than “you have to”.

• Look at the snow. It must be cold outside. (I’m sure)
• You haven’t eaten all day — you must be starving!
• The lights are out and nobody is at home. They must have gone out. (modal perfect — see §8)

The negative deduction is can’t (not “mustn’t”): “That can’t be Mike — he’s on holiday.”

7Should, ought to (and had better) A2

The advice family. Mild, not forceful. Should is the everyday default; ought to is its slightly more formal twin; had better adds an “or else” warning.

SHOULD — advice and expectation

OUGHT TO — the same idea, slightly more formal B1

• Do you think I ought to apply for this job? (= should I apply…?)
• Jack ought not to go to bed so late. (= shouldn’t go)
• It was a great party. You ought to have come. (= should have come)

In casual speech, should is much more common; ought to appears in writing or slightly formal contexts. They’re interchangeable for advice and expectation.

SHOULD vs MUST — how strong?

HAD BETTER — advice with a warning B2

Stronger than should — implies “or else there will be a problem”. Used for the present/near future, not general advice.

• You ‘d better leave now or you’ll miss the train. (urgent, with consequence)
• We ‘d better not be late — she gets really angry.
• You ‘d better see a doctor about that cough.

SHOULD HAVE — the regret machine B2

Past advice, after the fact. The action didn’t happen (or shouldn’t have).

• You missed a great party. You should have come! (you didn’t, but it would have been good)
• I should have studied harder — I failed the exam.
• I’m feeling sick — I shouldn’t have eaten so much. (I did, and now I regret it)
• She shouldn’t have been listening to our conversation. (continuous form — an action in progress)

More on this in §8 Modal Perfect — the past machine.

8Modal perfect — the past machine B2

Add have + past participle after any modal and you’ve travelled to the past. The pattern does three jobs: deduction, regret/criticism, and hypothetical past (the bridge to the third conditional).

The pattern

Job 1 — Deduction about the past

Same modal-strength dial as the present, but pointing backward.

• I didn’t see John yesterday. He might have stayed at home. (possible — guess)
• He wasn’t at the meeting. He might not have been feeling well. (continuous form)
• You haven’t found your keys? You could have left them at work.
• Her car isn’t here. She must have gone already. (certain — logical conclusion)
• That can’t have been Mike — he was on holiday. (certain it wasn’t)
• Sarah couldn’t have received my message. Otherwise she would have replied.

Job 2 — Regret & criticism

• I should have studied harder. (I didn’t — regret)
• You should have called — we were worried! (criticism)
• I shouldn’t have eaten so much chocolate. (I did — regret)
• You could have told me you were going to be late. (criticism — you didn’t, and I think you should have)
• I’m sorry — I could have helped you, but I didn’t realise.
• I needn’t have rushed — the train was delayed anyway. (I rushed but it was unnecessary)

Job 3 — Hypothetical past (3rd conditional bridge)

“What if…?” pointed backwards. The action did NOT happen.

• If I had bought BTC in 2016, I would have made a lot of money. (I didn’t buy it)
• If I had had time last summer, I could have gone on holiday. (I didn’t have time)
• If I had passed the IELTS some years ago, I wouldn’t be preparing for it now. (mixed conditional — past cause, present result)
• I wish you were more careful crossing the road — you could have got hurt!

For the deep dive on these patterns, see the dedicated Modal Perfect & Past Conditionals page.

Quick reference — modal perfect by modal

9Stacking & semi-modals B2

Rule 2 says you can’t combine two pure modals. But you absolutely can combine a modal with a semi-modal — that’s how English handles ideas like “future ability” or “possible obligation”.

The pure-modal short list

Pure modals: can, could, may, might, must, shall, should, will, would. Plus ought to (with to, but otherwise behaves like a pure modal).

Semi-modals: be able to, have to, need to, used to, be allowed to, be obligated to, be supposed to, be going to, had better, would rather, dare, want to, plan to, manage to.

Legal stacks — modal + semi-modal

The relay-runner table — same idea across tenses

USED TO — the semi-modal of past states / habits B1

• I used to live in Rome. (past state, no longer)
• She used to drink coffee, but she switched to tea.
• Question: Did you use to play football? (no “did you used to”)
• Negative: I didn’t use to like olives. (no “didn’t used to”)

10Common mistakes & decision flowchart

Top 10 mistakes — spot the error

Decision flowchart — what do you want to express?

11Practice — 10 worksheets

Type the answer in the blank, then click Check for instant feedback. Show reveals the answer; Reset clears the worksheet. Multiple correct answers are accepted where they exist.

More on modal perfect & past conditionals in the dedicated Past Machine deep-dive page.