MODAL VERBS
SHOULD/OUGHT TO
Advice/ opinion
we should/ ought to keep the sea clean
CAN/COULD/BE ABLE TO
Ability/Possibility.
I was able to install solar panels on the roof
Request
Can I join your group?
suggestion
Teachers can encourage students to ride bikes to school
MAY/MIGHT
Possibility
Peter may/might join Greenpeace
MUSTN'T
Prohibition
You mustn't waste water
Shall
Offer/ suggestion
Shall I help you with your environmental research?
MUST/HAVE TO
Obligation/ necessity
We have to/must avoid using plastic products
strong belief
Sam must feel terrible after seeing all that plastic in the river
DON'T HAVE TO/NEEDN'T
Lack of obligation/ necessity
You don't have/ needn't to worry about swimming here. This river is not polluted
CAN'T
Inability/ Impossibility
The mayor can't solve our pollution problem.
Prohibition
You can't throw plastic in this bin
Disbelief
That can't be Bob's car. He doesn't drive
Would
Formal request
Would you open the window, please?
Offer
Would you like some water?