We can use modal auxiliaries in a sentence however we like, they do not change their form.

Examples:

  • They do not have present participle form (modal auxiliary + ing)
  • They do not have past participle form (modal auxiliary + ed)
  • They do not take an s in the 3rd person singular (modal auxiliary + s)
 

Modal auxiliaries always come before the main verb. (Both the modal auxiliaries and main verbs are in bold.)

Examples:

  • Smoking can cause cancer.
  • The train could arrive anytime now.
  • She may get married next year.
  • We might reach there before it gets dark.
  • He will give us a lift to the circus.
  • I would hate to tell her the truth.
 

When we make negative statements with the word 'not', we place the modal auxiliaries before 'not'. We can use contraction (e.g. couldn't) of the modal verb (except may) and the negative not that follows it.

Examples:

  • We could not read his handwriting. / We couldn't read his handwriting.
  • She should not argue with her grandmother. / She shouldn't argue with her grandmother.
  • You must not bite your nail. / You mustn't bite your nail.
  • He ought not to be so rude to her. / He oughtn't to be so rude to her.
  • She may not like him at all. (Not: She mayn't like him at all.)
 

In yes-no questions, modal auxiliaries appear before the subject. In reply to the questions, the modal auxiliaries + not can be in shortened form.

Examples:

  • Can you play mahjong? Yes, I can. / No, I can't.
  • Will you help me wash my car? No, I won't.
  • Would you do that for me? No, I wouldn't.
  • Should I lend him the money? No, you shouldn't.
 

When there's an adverb in a sentence, the modal auxiliary comes before the adverb.

Examples:

  • I can just imagine your sister as a police officer.
  • Our team could yet win – you never know
  • He will soon be as tall as his father.
  • She would always turn her face away when she saw me.
  • You might still prove me wrong
  • I shall never forget your beautiful face.
  • You should just pretend you didn't hear it.