May / Might / Could
Three modals cover possibility and uncertainty — with subtle differences in formality and certainty. May is neutral and slightly formal (She may be able to join us later). Might is slightly less certain than may (I might apply for the role). Could expresses possibility or suggestion (This could be the opportunity we’ve been waiting for). The probability scale runs from won’t / can’t (0–10%) through might not / may not (30–40%), might / may / could (50–60%), should / ought to (70–80%), and will / must (90–100%). For past possibility, may have / might have / could have + past participle speculate about what happened (She might have missed the email).
This worksheet builds B1 fluency with the three possibility modals across present and past time, with a probability-scale analytical task.
Worksheet preview
What’s inside:
- Grammar Box with the three modals, the probability scale, and the past form (may/might/could have + past participle)
- Multiple-choice (8 items): choose the most appropriate modal based on the certainty implied
- Probability-scale task: assign a percentage to each statement and explain the reasoning
- Rewriting: convert speculation sentences (Perhaps she’s still at the office) into might / may / could form
- Full Answer Key plus Teacher Notes on the past-form rule (don’t drop have) and on register
Common mistakes addressed: dropping have in past speculation (She might missed it), using can for present possibility about a specific situation (He can be in the meeting room — wrong; He might / could be), and using the wrong modal for very high certainty (He could be late where will is meant).
For: Adult and teenage learners (14+) at CEFR B1, in intermediate classes, 1:1 lessons, or self-study. Possibility modals are tested in Cambridge B1 Preliminary (PET) and B2 First (FCE) — particularly in the Speaking parts, where speculation and deduction are recurring functional needs. Part of the Modal Verbs collection — the natural sibling is Must / Have To / Should, which sets up the obligation-modal system this contrasts with.
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