Modal verbs do not take an ‘s‘ for the third person singular.
She musts walk her home everyday. ❌ (wrong)
She must walk her home everyday.✔️ (correct)
After ‘can’, ‘could’, ‘may’, ‘might’, ‘shall’, ‘should’, ‘ought to’, ‘will’, ‘would’, ‘must’,‘have to’, we use a bare infinitive (i.e. an infinitive without ‘to’).
We do NOT use a past form of a verb nor an -ing form.
I could to swim when I was nine.❌ (wrong)
I could swim when I was nine.✔️ (correct)
The infinitive can be active. When necessary, it can be passive.
The robbers may be caught soon.
Your money may be found soon.
I think this radio can be repaired.
Check modal verbs list down below with exercises and free PDF.
Ability: Birds can fly. I can swim
Permission: Yes, you can go to the cinema.
He could ride my car, if he let me know earlier.
Permission: You may see your friends now.
Possibility: It may snow tomorrow.
She might be really sick.
Future actions: We shall visit again next time.
Responsibility: They should bring their books to school.
You ought to ask for your father’s permission.
Future Actions: She will join our team next month.
Imagination: I would call Mary if I remember her number.
Necessity: Human must eat.
Obligation: You must hand in your homework on time.
I have to help my mother tomorrow.
👉Modal verbs are always used in making requests, offers, permission and invitations.
Requests: Can you give me some water?
Asking people to do things: Could you wait her for a while?
Offering: Can I help you?
Offering/Inviting: Would you like a cup of tea?
Can I speak to Mohammad, please?
Could I ride your bike?
May I come in? (more formal/polite)
You can download more detailed modal verbs, exercises, examples free PDF down below.