Modal Verbs for Possibility: May, Might, Could (B1–B2 Guide)

Introduction

Imagine you are planning a weekend trip. You check the weather app and see “30% chance of rain.” How do you express this possibility in English? You need modal verbs like may, might, and could. These three small words help you sound natural and accurate when talking about things that are possible but not certain. In this post, you will learn exactly how to use them correctly, avoid common mistakes, and practise with real examples.

What Are Modal Verbs for Possibility?

Modal verbs for possibility are auxiliary verbs that we use to say how likely something is. The three main ones are may, might, and could. They all express that something is possible, but there are subtle differences in how certain you sound. For example:

• May suggests a moderate chance (around 50%).
• Might suggests a lower chance (around 30–40%).
• Could suggests a general possibility, often used in hypothetical situations.

These verbs are essential for B1 and B2 learners because they appear in everyday conversations, writing, and exams like IELTS or Cambridge.

Rules for Using May, Might, and Could

1. Use the base form of the main verb after the modal. Never add “to” or change the verb. Example: “She may come later.” (Not “may to come” or “may comes.”)
2. They do not change form for he/she/it. Unlike regular verbs, modals stay the same. Example: “He might be tired.” (Not “mights.”)
3. Use “not” to make negatives. Place “not” directly after the modal. Example: “They could not hear us.” Contractions: mayn’t (rare), mightn’t, couldn’t.
4. Form questions by inverting the subject and modal. Example: “May I borrow your pen?” / “Could this be true?”
5. Use “may” and “might” for present and future possibility. For past possibility, use “may have” or “might have” + past participle. Example: “She may have forgotten the meeting.”

How to Use May, Might, and Could Step by Step

Step 1: Choose the right modal based on certainty

Think about how sure you are. If you feel fairly sure (about 50% chance), use may. If you feel less sure (about 30–40%), use might. If you are just guessing or imagining a possibility, use could.

Example: “The train may be late due to weather.” (moderately likely) / “It might rain later.” (less likely) / “We could take a taxi if we miss the bus.” (hypothetical)

Step 2: Form the sentence correctly

Place the modal before the base verb. For negatives, add “not.” For questions, swap the subject and modal.

• Statement: “She may arrive early.”
• Negative: “She may not arrive early.”
• Question: “May she arrive early?”

Step 3: Use “have” + past participle for past possibility

When you want to say something was possible in the past, use may have, might have, or could have + past participle.

• “He may have missed the bus.”
• “They might have forgotten our appointment.”
• “She could have chosen a different career.”

Examples in Sentences

• “I may go to the party if I finish my homework.”
• “The package might arrive tomorrow, but I am not sure.”
• “We could visit the museum this weekend.”
• “She may not like the surprise.”
• “He might be the new manager.”
• “They could have taken the wrong train.”
• “May I use your phone?”
• “It might rain today, so bring an umbrella.”
• “The keys could be in the drawer.”
• “She may have already left for work.”
• “We might not have enough time.”
• “He could become a famous artist one day.”

Common Mistakes with May, Might, and Could

• Mistake 1: ❌ “She mays come.”
  ✅ “She may come.” (Modals never add -s.)
• Mistake 2: ❌ “He might to go.”
  ✅ “He might go.” (Use base verb without “to.”)
• Mistake 3: ❌ “I could to swim when I was young.”
  ✅ “I could swim when I was young.” (No “to.”)
• Mistake 4: ❌ “They may not to come.”
  ✅ “They may not come.” (Negatives use “not” directly after modal.)
• Mistake 5: ❌ “She might has forgotten.”
  ✅ “She might have forgotten.” (Use “have” not “has” after modals.)

Quick Summary

• May = moderate possibility (around 50%).
• Might = lower possibility (around 30–40%).
• Could = general or hypothetical possibility.
• Always use the base form of the main verb.
• No change for he/she/it.
• Negatives: add “not” after the modal.
• Past possibility: modal + have + past participle.

Practice Exercises

Fill in the blanks with may, might, or could (and sometimes “have” if needed).

1. “I __________ go to the cinema tonight, but I have to check my schedule.”
2. “She __________ have forgotten her wallet at home.”
3. “We __________ not finish the project on time.”
4. “He __________ be the best candidate for the job.”
5. “They __________ have taken a different route.”

Answers:

1. “I may go to the cinema tonight, but I have to check my schedule.”
2. “She might have forgotten her wallet at home.”
3. “We may not finish the project on time.”
4. “He could be the best candidate for the job.”
5. “They could have taken a different route.”

Conclusion

Now you understand how to use may, might, and could to express possibility in English. Remember the rules: use the base verb, no changes for he/she/it, and add “not” for negatives. Practise with the exercises above, and soon these modals will feel natural. Keep listening to how native speakers use them in movies, podcasts, and conversations.

FAQ

1. What is the difference between “may” and “might”?

May generally indicates a higher probability (around 50%), while might suggests a lower probability (around 30–40%). In everyday speech, many native speakers use them interchangeably, but for exams and formal writing, the nuance matters. For example, “It may rain” sounds more likely than “It might rain.”

2. Can I use “could” for past ability?

Yes, could can express past ability (e.g., “I could swim when I was five.”) But for past possibility, use could have + past participle (e.g., “He could have won the race if he had trained harder.”) Be careful not to confuse these two uses.

3. Is “may” more formal than “might”?

Generally, yes. May is often used in formal contexts, such as requests (“May I come in?”) or written notices (“Students may leave after 3 PM.”) Might is more common in casual conversation. However, both are grammatically correct in most situations.

4. How do I make a question with “might”?

To form a question with might, invert the subject and modal: “Might I borrow your pen?” This is quite formal and less common than using “may” or “could.” In everyday English, people usually say “Could I borrow your pen?” or “May I borrow your pen?”