Can, could, may, and might are among the most commonly confused modal verbs in English. Although they look similar, each one has a different meaning and purpose. In this guide, you’ll learn the differences, avoid common mistakes, and use them confidently in everyday English.
Have you ever paused while writing an email and wondered whether you should write:
- Can I review this document?
- Could I review this document?
Or perhaps you’ve asked yourself whether may and might mean exactly the same thing.
If so, you’re not alone.
These four small words cause confusion for many English learners because they often seem interchangeable. However, each one has its own purpose, and choosing the right word can make your English sound more natural, polite, and professional.
Over the years, I’ve noticed that many people understand the grammar rules but still struggle to choose the right modal verb in real-life situations. The good news is that once you understand the basic differences, using them becomes much easier.
Table of Contents
Free Printable Worksheet
Practise as you learn! Download the FREE Worksheet (PDF) on Can, Could, May, and Might and complete the exercises while reading this lesson.
In this guide, you’ll learn:
- when to use can and could
- when to use may and might
- how they affect the tone of your sentences
- common mistakes to avoid
- plenty of everyday examples
Let’s get started.
What Are Modal Verbs?
Can, could, may, and might are modal verbs.
A modal verb works together with a main verb to express ideas such as:
- ability
- permission
- possibility
- requests
- probability
Unlike ordinary verbs, modal verbs never describe the main action themselves. Instead, they change the meaning or tone of the main verb.
For example:
✅ She can speak English.
✅ We might finish early.
The Golden Rule of Modal Verbs
Modal verbs follow one very important rule.
They never change their form, regardless of the subject.
Correct:
- I can swim.
- He can swim.
- They can swim.
Not:
❌ He cans swim.
The verb after a modal must always be in its base form.
Correct:
- She can write.
- We could finish today.
Incorrect:
❌ She can writes.
❌ We could to finish.
Remember this rule and you’ll avoid many common grammar mistakes.
1. Can vs. Could
Although could is the past form of can, it has several additional uses.
A. Ability
Can = Present Ability
Use can to describe something you are able to do now.
Examples:
- I can read blueprints without my glasses.
- She can speak three languages.
- We can finish the report today.
Could = Past Ability
Use could for a general ability in the past.
Examples:
- When I was younger, I could stay awake all night studying.
- She could run very fast as a child.
- My grandfather could repair almost anything.
B. Requests and Permission
This is where tone becomes important.
Can = Casual
Use can with friends, family, classmates, or colleagues.
Examples:
- Can I borrow your pen?
- Can you send me that file?
- Can we start now?
These sound friendly and natural.
Could = More Polite
Use could when speaking to customers, clients, managers, teachers, or someone you don’t know well.
Examples:
- Could you please send me the progress report?
- Could I speak with the manager?
- Could you explain that again?
Using could makes your request sound more respectful.
C. Could for Possibility
We also use could to talk about possible situations.
Examples:
- The delivery could be delayed because of heavy rain.
- This solution could save us time.
- The meeting could finish earlier than expected.
Here, could suggests a possible outcome, not a certainty.
2. May vs. Might
Both may and might express possibility.
The main difference is that may usually suggests a stronger possibility, while might often suggests a more uncertain one.
However, in modern English, they are frequently interchangeable.
A. May = A Real Possibility
Use may when something seems reasonably likely.
Examples:
- It may rain this afternoon.
- We may launch the new website next week.
- The manager may approve your proposal.
B. Might = A Less Certain Possibility
Use might when you’re less certain or simply making a guess.
Examples:
- We might expand the project next year.
- I might go for a walk later.
- She might join us if she finishes work early.
Although might often sounds less certain than may, the difference is usually quite small in everyday conversation.
C. May for Formal Permission
May is traditionally used when asking or giving permission in formal situations.
Examples:
- May I come in?
- May I review the project plans?
- You may leave once the meeting has finished.
Today, many native speakers simply say Can I…? in everyday conversation, but May I…? still sounds more formal and polite.
Common Mistake: Maybe vs. May Be
Many learners confuse these two expressions.
Maybe (one word)
Means perhaps.
Examples:
- Maybe I’ll go tomorrow.
- Maybe she’s busy.
May be (two words)
Is a modal verb followed by the verb be.
Examples:
- The contractor may be delayed.
- The meeting may be cancelled.
A simple trick:
If you can replace it with perhaps, use maybe.
Quick Comparison Table
| Situation | Best Choice | Example |
|---|---|---|
| Present ability | Can | I can update the website today. |
| Past ability | Could | I could swim when I was five. |
| Casual request | Can | Can you help me? |
| Polite request | Could | Could you explain this? |
| Formal permission | May | May I leave early? |
| Likely possibility | May | It may rain later. |
| Less certain possibility | Might | We might visit next week. |
Frequently Asked Questions
Is it wrong to say “Can I…”?
Not at all.
In modern English, Can I…? is perfectly acceptable in everyday conversations.
However, Could I…? and May I…? sound more polite and are often preferred in formal situations.
Can “could” and “might” both express possibility?
Yes.
Both can describe possible situations.
For example:
- We could finish early.
- We might finish early.
Sometimes the difference is very small.
Generally, could often suggests that something is possible because the circumstances allow it, while might focuses more on uncertainty.
What mistakes should I avoid?
Remember these common errors.
Incorrect:
❌ She can sings.
Correct:
✅ She can sing.
Incorrect:
❌ I could to help you.
Correct:
✅ I could help you.
Incorrect:
❌ He cans swim.
Correct:
✅ He can swim.
A Simple Trick to Remember
Whenever you’re unsure which word to choose, ask yourself these questions:
- Is it happening now or in the past?
Present = can | Past = could - Am I speaking casually or formally?
Casual = can | Polite = could or may - Am I talking about a possibility?
More likely = may | Less certain = might
🎁 Free Printable Worksheet
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Final Thoughts
Although can, could, may, and might are only four small words, they play a big role in everyday English. They help you express ability, ask permission politely, make requests, and talk about possibilities with confidence.
The best way to master them is through regular reading, listening, and practice. As you notice these modal verbs in books, emails, and conversations, ask yourself why the speaker or writer chose that particular word.
With time, choosing the right modal verb will become second nature—and your English will sound more natural, accurate, and confident.