Modal verbs such as should, must, can, may, could, have to and be able to are used to express meanings like advice, necessity, ability, permission, and obligation. They are often used with other verbs and have specific rules regarding forms, negatives and questions. For example, must expresses strong obligation or necessity, such as "Students must get a 5 to pass the test". Should gives advice or makes suggestions as in "You should wear a coat". Have to and must both denote obligation but have to refers to external obligation while must refers to internal views.

1. Modal VerbsModal Verbs
Should / Shouldn’tShould / Shouldn’t
Must / Mustn’tMust / Mustn’t
Can / Can’tCan / Can’t
May / Might / Might notMay / Might / Might not
Could / Couldn’tCould / Couldn’t
Have to / Don’t have toHave to / Don’t have to
Be able toBe able to

2. Modal verbsModal verbs: differences: differences
with normal verbswith normal verbs
RULESRULES EXAMPLESEXAMPLES
No –sNo –s in the 3rd person ofin the 3rd person of
the Present Simple tense.the Present Simple tense.
HeHe mustmust go to the doctor.go to the doctor.
Negatives and questionsNegatives and questions
without do / doeswithout do / does..
II can’tcan’t (can not) speak Chinese.(can not) speak Chinese.
CouldCould you swim when you wereyou swim when you were
four years old?four years old?
They go with another verbThey go with another verb
in bare infinitive.in bare infinitive.
YouYou shouldshould buybuy a new pair ofa new pair of
shoes.shoes.
Many modal verbs do notMany modal verbs do not
have past or future forms.have past or future forms.
WeWe will canwill can go to the cinemago to the cinema
tomorrow.tomorrow.

3. USE:USE: Should / Shouldn’tShould / Shouldn’t
 ToTo give advicegive advice (donar(donar
consells):consells):
 ToTo make suggestionsmake suggestions
(fer suggeriments):(fer suggeriments):
– You should buy thisYou should buy this
dress, it is verydress, it is very
beautiful.beautiful.

4. USE:USE: mustmust
 To expressTo express necessitynecessity,, strongstrong
recommendationrecommendation oror obligationobligation::
– You must be quiet in the library.You must be quiet in the library.
– You must protect your skin with suncream.You must protect your skin with suncream.
– Students must get a 5 to pass the EnglishStudents must get a 5 to pass the English
test.test.
1 2 3

5. USE:USE: mustmust
 To expressTo express certainty that something iscertainty that something is
true:true:
– You must be John’s son.You must be John’s son.

6. USE:USE: mustn’tmustn’t
 To express thatTo express that
something issomething is
forbiddenforbidden (prohibited)(prohibited)
oror wrongwrong

7. USE:USE: can / can’tcan / can’t
 To expressTo express abilityability (habilitat, saber fer),(habilitat, saber fer),
possibilitypossibility, to ask for and give, to ask for and give permissionpermission,,
and to makeand to make requestsrequests andand offersoffers (demanar(demanar
i oferir):i oferir):
– Can we play Wii this afternoon?Can we play Wii this afternoon?
– We can go home by car.We can go home by car.
– Susan can play the guitar.Susan can play the guitar.
– Can I help you?Can I help you?
– Can I go to the toilet, please?Can I go to the toilet, please?

8. USE:USE: can’tcan’t
 To expressTo express certainty that something is notcertainty that something is not
possiblepossible::
– He can’t be our new coach.He can’t be our new coach.

9. USE:USE: may (not)may (not)
 To expressTo express possibility:possibility:
– We may go to the beach this weekend.We may go to the beach this weekend.
 To make a politeTo make a polite requestrequest oror offer:offer:
– May I take a sweet?May I take a sweet?

10. USE:USE: might (not)might (not)
 To express a remoteTo express a remote possibility:possibility:
– We might go on holidays to New York thisWe might go on holidays to New York this
year.year.

11. USE:USE: could / couldn’tcould / couldn’t
 To express ability and possibility,To express ability and possibility, in thein the
pastpast::
– CouldCould you play the piano when you wereyou play the piano when you were
four?four?
– The weather was bad yesterday so weThe weather was bad yesterday so we
couldn’tcouldn’t go to the beach.go to the beach.
 To make suggestions and polite requests:To make suggestions and polite requests:
– WeWe couldcould go to the zoo tomorrow.go to the zoo tomorrow.
– CouldCould I borrow your pencil, please?I borrow your pencil, please?

12. Have to: FORMHave to: FORM
 Have toHave to can be considered acan be considered a semi-modalsemi-modal
verb because it is a little bit different:verb because it is a little bit different:
– The 3rd person singular is made withThe 3rd person singular is made with hashas::
 SheShe has tohas to do her homework.do her homework.
– The negative form is made withThe negative form is made with do / doesdo / does::
 YouYou don’t have todon’t have to wear a tie to come to classwear a tie to come to class..
– It can be used in past and future tenses:It can be used in past and future tenses:
 II had tohad to go to the hairdresser last week.go to the hairdresser last week.

13. USE:USE: have tohave to
 To expressTo express obligationobligation oror necessitynecessity::
– MikeMike has tohas to turn in a project tomorrow.turn in a project tomorrow.

14. USE:USE: don’t / doesn’t have todon’t / doesn’t have to
 To express that something isTo express that something is notnot
necessarynecessary::

15. What is the difference betweenWhat is the difference between
have tohave to andand must?must?
 To express that the obligation / necessityTo express that the obligation / necessity
comes from the speaker’s point of view wecomes from the speaker’s point of view we
useuse must:must:
– II mustmust stop smoking (I want to, it is mystop smoking (I want to, it is my
decision)decision)
 To express that the obligation / necessityTo express that the obligation / necessity
comes from outside we usecomes from outside we use have to:have to:
– II have tohave to stop smoking (the doctor says it).stop smoking (the doctor says it).

16. Be able to: FORMBe able to: FORM
 Be able toBe able to can be considered acan be considered a semi-semi-
modalmodal verb, too:verb, too:
– The verbThe verb to beto be is used in all its forms andis used in all its forms and
tenses:tenses:
 John was able to catch the train on time.John was able to catch the train on time.
 Will you be able to buy some bread?Will you be able to buy some bread?
 She has never been able to swim for 60 minutes.She has never been able to swim for 60 minutes.

17. Summary: Use of modal verbsSummary: Use of modal verbs
ShouldShould
Shouldn’tShouldn’t
AdviceAdvice YouYou shouldshould wear a coat.wear a coat.
SuggestionsSuggestions YouYou shouldshould buy this dress.buy this dress.
MustMust NecessityNecessity StudentsStudents mustmust get a 5 to pass the test.get a 5 to pass the test.
StrongStrong
recommendationrecommendation
YouYou mustmust protect your skin withprotect your skin with
suncream.suncream.
ObligationObligation YouYou mustmust be quiet in the library.be quiet in the library.
Mustn’tMustn’t ProhibitionProhibition YouYou mustn’tmustn’t cross the street in a redcross the street in a red
light.light.
SomethingSomething
wrongwrong
YouYou mustn’tmustn’t shout to your parents.shout to your parents.
CanCan
Can’tCan’t
AbilityAbility II can’tcan’t speak Chinese.speak Chinese.
PossibilityPossibility WeWe cancan go home by car.go home by car.
PermissionPermission YouYou cancan watch TV now.watch TV now.

18. Summary: Use of modal verbsSummary: Use of modal verbs
CouldCould
Couldn’tCouldn’t
Ability in theAbility in the
pastpast
II couldcould play the piano when I was four.play the piano when I was four.
Possibility in thePossibility in the
past.past.
WeWe couldn’tcouldn’t go to the beach because itgo to the beach because it
was cloudy.was cloudy.
Polite requestsPolite requests CouldCould I have a cup of coffee, please?I have a cup of coffee, please?
SuggestionsSuggestions WeWe couldcould go to the zoo tomorrow.go to the zoo tomorrow.
Have toHave to Obligation /Obligation /
NecessityNecessity
MikeMike has tohas to turn in a project tomorrow.turn in a project tomorrow.
Don’t /Don’t /
Doesn’tDoesn’t
have tohave to
Something notSomething not
necessarynecessary
YouYou don’t havedon’t have to bring anything to theto bring anything to the
party (but you can).party (but you can).