Modal verbs are different from normal verbs:
1: They don't use an 's' for the third person singular.
2: They make questions by inversion ('she can go' becomes 'can she go?').
3: They are followed directly by the infinitive of another verb (without
'to').
Modal verbs are used to express:
Ø Probability or possibility: to say how sure we are that something happened / is happening / will
happen.
1: Talking about the
present:
• She must be on the bus. (I'm fairly sure this is a good guess)
• She could be lost. (maybe)
• She may be in the wrong room. (maybe)
• She might come soon. (less probable than may) / past of may
• She can't be at home. (I'm fairly sure this isn't true)
Ø Ability
1: Talking about the present: can / can't (for both general and specific ability)
• He can't drive.
• We can come now.
2: Talking about the past:
could / couldn't (for general ability)
• I could read when I was four.
was or were able to / couldn't (for specific ability)
• She was able to pass the exam, even though she hadn't
studied much.
• I couldn't open the window.
3: Talking about the
future:
will / won't be able to (general ability)
• At the end of the course, you will be able to make your own website.
Ø Permission / Requests we can use verbs
such as 'can', 'could' and 'may' to ask for and give permission. We also use
modal verbs to say something is not allowed.
• Might/May I come in?
/ May I call you later? (very polite)
• Could I leave early today,
please?
/ Could I have a coke, please? (polite)
• Can we swim in the lake? / Can you lend me your pencil, please? (informal)
Obligation, Prohibition and Advice
modal verb | Positive | Negative |
have to / don't have to (had to: for the past)/ don't need to | obligation (possibly from outside) • Children have to go to school. • She has to pay a fine. | no obligation = don´t need to/ have to • She doesn't have to work on Sundays. • You don't need to eat anything you don't like. |
must / mustn't | strong obligation (possibly based on the speaker's opinion) • I must study today. | prohibition • You mustn't smoke here. |
should / shouldn't | advice • You should save some money. | advice • You shouldn't smoke so much. |
Exercise 2: Modals of possibility