Forming Passives With Modals 

Affirmative Form	Object + may, must, can, could, ought to, should + be + verb3
Question Form	Must, may, can, should, might + object + be + verb3 (past participle)

Something must / can / should... be done by someone at sometime.

Active : Our English teacher may give an exam today.

Passive: An exam may be given by our English teacher today.

Active : Thomas has written many books.

Passive: Many books have been written by Thomas.

Active : Do you have to pay the bill before leaving the restaurant?

Passive: the bill have to be paid before leaving the restaurant?

Active : Juan can give them some information about the job.

Passive: Some information can be given about the job by Juan.

Passive2: They can be given some information about the JOB by Juan.

Active : You must obey the traffic rules.

Passive: The traffic rules must be obeyed.

Quick Exercise

Put the following sentences into passive voice. (Modals)

1.      Active : We may ask him a few questions.

         Passive  : A few questions may be asked by him.

2.      Active : I can manage a motor car.

         Passive : A motor car can be managed

3.      Active : You must inquire the way.

         Passive : The way must be inquired.

4.      Active : He might give you a chance.

         Passive : A chance might be given.

5.      Active : I could show you his house if you would permit me.

        Passive : His house can be shown to you if you would permit

6.      Active : I should enjoy a sea-voyage.

        Passive : A sea-voyage should be enjoyed.