There are 9 main modal verbs in English which have many different functions. Here are just a few of the common uses:
|Can||I can swim.||present ability||We can watch TV.||permission||Paris can be very hot.||occasional possibility|
|Could||I could swim.||past ability||We could watch TV.||past permission||We could go out.||making suggestions||It could rain later||future possibility|
|Might||It might rain later.||future possibility||He might be French.||present possibility|
|May||You may watch TV.||permission||It may rain later.||possibility|
|Must||I must go home.||obligation||He must be angry.||deduction|
|Will||I'll answer the phone.||spontaneous decision||He'll be late.||prediction||I'll kill him!||threat/promise||I'll help you.||offer|
|Would||I'd never kill someone.||hypothesising||I'd often watch TV.||past habits|
|Shall||Shall we go home?||making suggestions||I shall be late.||prediction (formal)|
|Should||You should rest.||advice||He should be asleep.||expectation|
Note: the negatives don't always mean the exact opposite of the positive forms. You can learn more about this on the pages for the different functions.
You can never use two modal verbs together.
I will must stop smoking before I'm 30. X
Fortunately, most modal verbs have expressions with a similar meaning which you can use instead.
I will have to stop smoking before I'm 30. ✓
After a modal verb we use an infinitive without 'to'.
I must to go home now. X
I must go home now. ✓
However, many similar expressions are used with 'to'.
Ihome now. ( = should go)
Ihome now. ( = must go)
I used to eat lots of cake. ( = would eat)
I 'm not allowed to drink beer. ( = can't drink)
Next Lesson: Modals of ability