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Modal verbs Adapted from: "A Practical English Grammar", by A.J. Thomson and A.V. Martinet.

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• Complete the chart with your own examples, in English and in Spanish.
  Write a different example with a clear context for each modal verb form in the chart.
  
  
• Remember: for this chart to be useful to you, you need to practise with it.
  For example, if you want to write an example about possibility, think of something that is impossible, then use that as the context for your example:
  
  It is impossible to ski in August in Spain, but you can ski in Finland.
  
  Contrast this with "can" used for permission:
  
  You are not allowed to smoke in a school, but you can smoke in the street.
  
  
• You can also copy your examples from a good grammar or an Internet page. If you make up your own examples, you can hand them in on paper or e-mail them to your teacher for correction.

can could be able to	ability	«Can» or «am/is/are able to» are used for ability in the present. «Could» or «was/were able to» are used for ability in the simple past. «Could» or «would be able to» are used for the conditional. «Will be able to», «have been able to», etc. are used in all other tenses.	Examples:
may might could can	possibility	«May», «might» and «could» express possibility (meaning it is probable or likely) in the present. «May have» and «might have» express possibility (meaning it is probable or likely) in the past. «Can» expresses possibility (meaning it is possible or feasible) in the present. «Could have» express possibility (meaning it was possible or feasible) in the past.
must have to had to can't couldn't	deduction	«Must» and «have to» express certainty in the present. «Had do» expresses certainty in the past. «Can't» and «couldn't» express negative certainty. «Must have», «can't have» and «couldn't have» are used for deduction about past events.
will should	assumption (=supposition)	«Will» and «should» express a supposition or assumption, in the present or the future. «Will have» and «should have» express a supposition or assumption in the past. «Will» expresses more certainty than «should». «Ought to» is also possible, but not as common as «should».
must have to need should ought to need (to)	obligation	«Must», «have to», «need», «should» and «ought to» express obligation or necessity in the present. «Had to», «should have» and «ought to have» express obligation in the past. «Must» expresses the speaker's authority, «have to» expresses an external authority (but «must» is never used in the past, so «had to» can express both types of authority). «Mustn't» expresses prohibition. «Do/does not have to», «do/does not need to» or «needn't» express absence of obligation in the present. «Did not have to», «did not need to» or «needn't have» express absence of obligation in the past.
should ought to must shall	advice, offers & suggestions	«Should» and «ought to» are used to give or ask for advice. «Must» can be used to express emphatic advice. «Wh-word + should I/we» are used to ask for advice only. «Wh-word + shall I/we» is used to ask for advice or instructions. «Shall I» is used to make an offer. «Shall we» is used to make a suggestion.
should have could have might have	reproach	«Should have», «could have» and «might have» are used to express reproach. «Should have» can sound quite friendly, but «could have» and «might have» express a complaint. «Shouldn't have» is the only one that can be used in the negative.
could can may might be allowed to	permission	«Can», «could», «may», «might» and «am/is/are allowed to» are used to ask permission in the present. «May» and «can» are used to grant or deny permission in the present. «Could» is the most frequent, «can» is the most colloquial, «may» is more formal, «might» expresses more uncertainty. «Could» and «was/were allowed to» are used for permission in the past.
can could will would	requests	«Can you», «could you», «will you» and «would you» are used to ask someone to do something. «Can you» is the most colloquial one; «could you» is more polite; «will you» is the least polite one; «would you» is the most formal one. To ask for a thing you can also use «can I have», «could I have», «may I have» and «might I have».
would will	invitations	«Would you» and «will you» are used to invite someone to do something.
used to would	past habits	«Used to» and «would» are used to describe past habits which are not maintained in the present, or routines in the past which may or may not be kept in the present. «Used to» can also describe past states which are not the same in the present.