Modal Verbs

Modal verbs are auxiliary verbs that express ability, possibility, permission, obligation, and other meanings. They are followed by the base form of the main verb (without "to").

Characteristics of Modal Verbs

• No -s in third person singular: He can swim (not "cans")
• No infinitive form: There's no "to can"
• Questions formed by inversion: Can you help me?
• Negatives formed with "not": I cannot come.

CAN / COULD

Ability

Can (present ability):

• I can speak three languages.
• She can play the piano very well.

Could (past ability):

• When I was young, I could run very fast.
• He could solve difficult math problems.

Permission (informal)

• Can I use your phone?
• Could I borrow your car? (more polite)

Possibility

• It can get very cold in winter here.
• That could be the solution to our problem.

Requests

• Can you pass the salt? (informal)
• Could you help me with this? (more polite)

MAY / MIGHT

Permission (formal)

• May I come in?
• Students may use the library until 9 PM.

Possibility

May (50% possibility):

• It may rain tomorrow.
• She may be at home now.

Might (less than 50% possibility):

• I might go to the party if I finish my work.
• This might not be the right answer.

Polite requests

• May I ask you a question?
• Might I suggest a different approach?

MUST / HAVE TO

Obligation/Necessity

Must (strong obligation, often personal opinion):

• I must finish this report today.
• You must see this movie - it's fantastic!

Have to (external obligation):

• I have to work late tonight. (my boss said so)
• Students have to wear uniforms at this school.

Prohibition

Must not/mustn't:

• You mustn't smoke in the hospital.
• Children must not play with matches.

Logical deduction

• She's not answering her phone. She must be in a meeting.
• You've been working all day. You must be tired.

SHOULD / OUGHT TO

Advice/Recommendation

• You should see a doctor about that cough.
• Students ought to study more for better grades.

Expectation

• The train should arrive at 3 PM.
• This ought to be an interesting meeting.

Criticism/Regret

• You should have told me earlier.
• I ought to have studied harder for the exam.

WOULD

Polite requests

• Would you mind closing the window?
• Would you like some coffee?

Hypothetical situations

• If I won the lottery, I would travel the world.
• What would you do in this situation?

Past habits

• When I was a child, I would visit my grandparents every summer.
• He would always arrive late to meetings.

Preferences

• I would rather stay home tonight.
• Would you prefer tea or coffee?

WILL

Future predictions

• It will be sunny tomorrow.
• The meeting will start at 2 PM.

Decisions made at the moment

• I will have the chicken, please.
• Don't worry, I will help you.

Promises

• I will call you tomorrow.
• We will finish the project on time.

Offers

• Will you have some more cake?
• I will carry that for you.

SHALL

Formal future (mainly British)

• We shall meet again soon.
• I shall never forget this day.

Offers/Suggestions

• Shall I help you with that?
• Shall we go to the cinema tonight?

Degrees of Certainty

Most certain → Least certain:

1. Must - I'm almost certain this is true
2. Will - I'm confident this will happen
3. Should/Ought to - I expect this to be true
4. Can/Could - This is possible
5. May - 50% possibility
6. Might - Less than 50% possibility

Modal Perfect Forms

Used to talk about past situations:

Could have + past participle

• You could have been hurt! (but you weren't)
• I could have told you earlier. (but I didn't)

Should have + past participle

• You should have studied harder. (but you didn't)
• I should have brought an umbrella. (but I didn't)

Must have + past participle

• She must have forgotten about the meeting. (logical deduction)
• They must have arrived already. (I'm almost certain)

Might have + past participle

• He might have missed the train. (possibility)
• She might not have received the message. (possibility)

Common Mistakes

1. Using infinitive "to" after modals

• Incorrect: I can to swim.
• Correct: I can swim.

2. Adding -s to modals in third person

• Incorrect: She cans speak French.
• Correct: She can speak French.

3. Using double modals

• Incorrect: I might could help you.
• Correct: I might be able to help you.

4. Wrong negative forms

• Incorrect: I don't can swim.
• Correct: I can't swim.

Interactive Practice Exercises

Choose the correct modal verb for each sentence. Type your answers and get instant feedback: