A modal verb is used with other verbs to express actions, events or situations that exist only as conceptions of the mind - permissions, possibilities, certainty, ability, wishes,obligations etc.
A modal verb is an auxiliary verb that can be used to change the grammatical mood of a sentence.
The key way to identify a modal verb is by its defectiveness (they have neitherparticiples nor infinitives).
・shall and should
・will and would
・may and might
・can and could
The following are not modal verbs but may be used for a similar purpose
・ought to and had better
・dare and need
・be able to
Characteristics of Modal Verbs
1.They have no –s in the third person singular.
・She can speak French. (correct)
2.Modal auxiliaries do not have infinitives or participles .
You cannot say shalling, shalled, to shall, to must or to may.
3. They take negation directry.(add "not")
・can not (can't)
・could not (couldn't)
・will not (won't)
・would not (wouldn't)
・may not (mayn't)
・might not (mightn't)
・shall not (shan't)
・should not (shouldn't)
・must not (mustn't)
4. They are followed by the “*bare infinitive”
*A bare infinitive is an infinitive without "to"
5. Their interrogation is to invert the subject and modal verbs.
・You can swim well.
・Can you swim well?
・I may go to the party.
・May I go to the party?
6. They can’t co-occur (go with).
・You may can go.
Position of Modal Verbs
Modal verbs always appear in the first position at the beginning of the verb phrase in English.
Unlike other verbs, modal verbs do not show tense or number. The eight possible verb phrase combinations that contain modal verbs in English are:
1.modal verb + base form = will see
2.modal verb + be + present participle = will be seeing
3.modal verb + have + past participle = will have seen
4.modal verb + be + past participle = will be seen
5.modal verb + have + been + present participle = will have been seeing
6.modal verb + have + been + past participle = will have been seen
7.modal + be + being + past participle = will be being seen
8.modal verb + have + been + being + past participle = will have been being seen
Function of Modal verb
Some of the more common definitions (in no particular order) of the modal verbs in English are:
can – ability, permission, possibility, request
could – ability, permission, possibility, request, suggestion
may – permission, probability, request
might – possibility, probability, suggestion
must – deduction, necessity, obligation, prohibition
shall – decision, future, offer, question, suggestion
should – advice, necessity, prediction, recommendation
will – decision, future, intention, offer, prediction, promise, suggestion
would – conditional, habit, invitation, permission, preference, request, question, suggestion