Usage	Modal Verb	Example
Ability	Can, could (past ability)	She can hold her breath for two minutes.
Possibility	Might, may, can, could	They might be late.
Permission	Can, could (more polite), may (most polite)	Could my son use your bathroom?
Obligation	Must, have to, need to	They need to check in by seven.
No obligation	Don’t have to, don’t need to	You don't have to take your shoes off.
Advice	Should, ought to	You should try online dating.
Habits	Will, would (past habits) + an adverb of frequency	They would sometimes take the train.
Preferences	Would rather	She would rather walk.

Modals in the Active Voice	Modals in the Passive Voice
They can do it.	It can be done.
You could sell your car.	Your car could be sold.
He might fix the refrigerator.	The refrigerator might be fixed by him.
They may make a donation.	A donation may be made by them.
You must finish this today.	This must be finished today.
He has to send that email.	That email has to be sent by him.
They need to find that document.	That document needs to be found by them.
She should fix her writing.	Her writing should be fixed.

Modals in the Past	Modals in the Past Passive
I should have started a job.	The job should have been started by me.
He must have paid the money.	The money must have been paid by him.
She may have eaten the meal.	The meal may have been eaten by her.
He might have fixed the refrigerator.	The refrigerator might have been fixed by him.
You ought to have spoken the truth.	The truth ought to have been spoken by you.

Change the following into passive voice.

The policeman should do a good job.

A good job should be done by the policeman.

1. We must paint our room.

2. They can’t repair our car.

3. Someone must install the new programme.

4. They should feed the dog once a day.

5. Mary can’t solve this exercise.

6. They should publish a new book.

7. We must inform him about the news.

8. We should discuss the matter again.

9. They cannot build a new bridge.

10. He used to make coffee every morning.

11. Tom may buy a new computer.

12. Laura might not invite Tina to the party.

13. Karen has to prepare dinner for everyone.

14. We needn’t do our homework now.

15. She used to clean the house every day.

Change from Active Voice to Passive Voice.

John should have done this.

This should have been done by John.

1. Mark can’t have stolen the money.

2. We should have informed the police.

3. Maria might have made a mistake.

4. The truck could have killed you.

5. He might have painted this picture before the war.

6. The police must have arrested the criminal by now

7. They should have called the doctor immediately.

8. She can’t have invited her former husband.

9. The fire may have damaged the house.

10. He must have paid the electricity bill.

11. He might not have enjoyed the party.

12. Someone should have set the alarm.

13. Someone could have texted her.

14. You should have told me that yesterday.

15. I may have sent the wrong package.

Passive of Modal Verbs