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Few modal pairs trip learners up quite like "may" and "might." They live in the same neighborhood of meaning — each one signals that something is possible rather than certain — yet swapping them can shift the tone of a sentence, change how hypothetical it feels, or make a polite request sound stiff. "May" still does heavy lifting when you ask or grant permission in formal settings, while "might" leans into imagined or unlikely outcomes. This guide walks through every role these two verbs play, where they overlap, and where they quietly part ways.
Table of Contents
Expressing Possibility With Either Verb
Both verbs tell your listener the same basic thing: something could be true or could happen, but you're not ready to commit. In casual speech, you can usually pick either one without changing the message.
The meeting may run late. / The meeting might run late.
Dad may already know. / Dad might already know.
We may drive out to the coast next weekend. / We might drive out to the coast next weekend.
The bakery may open late on Mondays. / The bakery might open late on Mondays.
Across those pairs, meaning barely budges. Each sentence acknowledges doubt — the speaker isn't sure and is simply flagging the chance.
How Likely Is "Likely"?
Some usage guides argue that "may" sits a notch higher on the probability scale than "might" — closer to a coin flip, whereas "might" slides toward the unlikely end. Native speakers don't really police this line, and in conversation you'll hear them used as twins. The chart below shows roughly where the major modals fall.
| Modal | Approximate Probability | Example |
|---|---|---|
| will | ~95-100% certain | The package will arrive Tuesday. (I'm confident.) |
| should / ought to | ~80-90% expected | The package should arrive Tuesday. (I expect so.) |
| may | ~40-60% possible | The package may arrive Tuesday. (It's a real option.) |
| might / could | ~20-40% possible | The package might arrive Tuesday. (There's an outside chance.) |
Practical Advice: Don't lose sleep over the probability split between these two. Either one gets the job of "it's possible" done. What actually matters: (1) reach for "may" when you're asking or granting formal permission, and (2) reach for "might" when the situation is hypothetical or contrary to fact.
Using May to Ask and Grant Permission
When the setting is polite, professional, or traditional, "may" is the go-to for permission questions and approvals. It carries more weight than "can" and is the verb teachers, hosts, and officials tend to use.
Requesting Permission
May I join you at this table? (polite)
May I speak for a moment? (common in meetings or classrooms)
May I borrow your pen? (courteous)
May I have the check, please? (polite restaurant request)
Giving or Refusing Permission
You may begin the exam now. (permission granted)
Guests may use the pool until 10 p.m. (allowed)
Employees may not record internal meetings. (formal prohibition)
What About "Might" for Permission? Centuries ago "might" did pull this duty as the past of "may," but today the usage survives only in very stilted contexts. Saying "Might I trouble you for a word?" sounds like something out of a Victorian novel. Stick with "may" in formal situations and "can" when you're among friends.
Talking About the Past: May Have / Might Have
When you want to guess about something that already happened, pair either modal with "have" plus a past participle. Both structures mean you're uncertain whether the event took place.
Jamie may have forgotten his keys. (Maybe he left them behind.)
The package might have arrived while we were out. (It's possible.)
They may have already finished dinner. (Perhaps they're done.)
The message might have ended up in the spam folder.
Might Have for Unreal Past Outcomes
Third-conditional sentences describe something that didn't actually happen. In those, "might have" feels far more natural than "may have" because you're talking about an imaginary result, not genuine uncertainty.
If I had known about the storm, I might have stayed home. (imagined outcome)
Had he trained properly, he might have finished the marathon.
The Negative Forms Compared
Put "not" after either modal and you get a negative guess — a statement that something possibly won't happen or isn't true. Don't mix these up with "must not," which forbids something outright, or "can't," which denies the possibility entirely.
Mia may not make it to dinner. (Possibly she won't come.)
The delivery might not arrive before noon. (A chance it's late.)
We may not have room for everyone in the car. (Possibly not.)
That strategy might not pay off. (It could flop.)
Contraction Note: "Mayn't" isn't a thing in modern English — you'll only spot it in older books. "Mightn't" exists, but it's mostly British and even there it's rare. Americans almost always spell out "might not."
Where "May" Shines in Formal English
Beyond permission, "may" covers several formal territories that "might" simply doesn't. You'll run into these patterns in written prose, public addresses, ceremonies, and academic work.
Blessings and Good Wishes
May your journey be safe and swift.
May peace be with you.
May the better candidate win.
May this new chapter bring you joy.
Concessive Clauses in Academic and Formal Writing
The proposal may sound ambitious, yet the data support its feasibility.
Although the findings may appear counterintuitive, they align with earlier research.
Quick Reference Table
| Feature | May | Might |
|---|---|---|
| Possibility | Yes — leans slightly more likely | Yes — leans slightly less likely |
| Permission | Yes — the formal choice | Archaic, almost never used |
| Wishes and blessings | Yes: "May you prosper" | No |
| Hypothetical scenarios | Feels awkward | The natural fit: "If I asked, I might learn" |
| Past speculation | may have + past participle | might have + past participle |
| Register | More formal | A touch more casual |
| Contracted negative | None in modern use | mightn't (rare, chiefly British) |
Slip-Ups Worth Watching For
Slip 1: Dropping "May" Into a Hypothetical
Awkward: If I trained every day, I may win the tournament.
Smoother: If I trained every day, I might win the tournament. (unreal → "might")
Slip 2: Mixing Up "May Not" and "Must Not"
"May not" = possibly won't: He may not call tonight. (Maybe he won't.)
"Must not" = forbidden: Visitors must not cross the barrier. (It's banned.)
Slip 3: Reaching for "Might" in a Formal Permission Request
Stilted: Might I take the afternoon off?
Natural: May I take the afternoon off? / Could I take the afternoon off?
Slip 4: Writing "May Of" or "Might Of"
Incorrect: He may of missed the train.
Correct: He may have missed the train.
Try It Yourself
Exercise 1: Fill in May, Might, or May/Might Have
1. ___ I borrow your laptop for a minute? (formal permission)
2. The road ___ be icy tonight — drive carefully. (possibility)
3. If she had called a cab, she ___ ___ caught the flight. (unreal past)
4. The lights are off. They ___ ___ gone out for the evening. (past possibility)
5. ___ your new home be filled with laughter! (formal blessing)
Answer Key
1. May I borrow your laptop?
2. The road may / might be icy tonight.
3. If she had called a cab, she might have caught the flight.
4. They may / might have gone out for the evening.
5. May your new home be filled with laughter!
Takeaways
Keep the big picture in mind: "may" and "might" both label something as possible, and most of the time either one will do. The meaningful splits come at the edges — "may" handles polite permission, formal wishes, and concessive writing, while "might" owns the territory of hypothetical and contrary-to-fact situations. Pair either with "have" plus a past participle to speculate about what already happened, and keep "may not" (a guess) clearly separate from "must not" (a rule). Once those patterns click, you'll choose between the two without thinking, matching both your meaning and the tone of the moment.
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