Modal auxiliary verbs do not have infinitives or participles

 Modal auxiliary verbs do not have infinitives or participles, but they can be combined with other verbs to form various expressions that convey different meanings. Here are some of the most common expressions with modal auxiliary verbs:

1. Modal + base verb (e.g. can swim, should go, must study)

• I can swim very well.
• You should go to bed early tonight.
• She must study for the exam tomorrow.

2. Modal + have + past participle (e.g. should have gone, could have done, might have seen)

• He should have gone to the meeting yesterday.
• We could have done better on the test.
• She might have seen the movie already.

3. Modal + be + present participle (e.g. must be working, might be sleeping, should be studying)

• He must be working late tonight.
• She might be sleeping now.
• You should be studying instead of watching TV.

4. Modal + have + been + present participle (e.g. could have been sleeping, must have been studying, might have been working)

• They could have been sleeping when we arrived.
• He must have been studying all night.
• She might have been working on the project.

Here are some exercises to fill in the blanks with the appropriate expression:

1. You ___________ studying for the exam instead of watching TV. (should/could/must)
2. She ___________ the answer to the question, but she wasn't sure. (might/could/should)
3. They ___________ better on the test if they had studied more. (could have/might have/should have)
4. I ___________ finished the project by now, but I've been busy with other things. (might have/could have/should have)
5. He ___________ the movie already, but he doesn't remember the ending. (could have/might have/should have been)

Answers:

1. should be
2. might know
3. could have done
4. could have
5. might have seen