MODAL AUXILIARIES

Modal Auxiliary Verbs

What are "modal auxiliary verbs"?

The verbs can, could, will, would, should, may, might, must, ought and shall are verbs which 'help' other verbs to express a meaning: it is important to realize that these "modal verbs" have no meaning by themselves. A modal verb such as would has several varying functions; it can be used, for example, to help verbs express ideas about the past, the present and the future. It is therefore wrong to simply believe that "would is the past of will": it is many other things.

The modal verbs include can, must, may, might, will, would, should. They are used with other verbs to express ability, obligation, possibility, and so on. Below is a list showing the most useful modals and their most common meanings:

Modal	Meaning	Example
can	to express ability	I can speak a little Russian.
can	to request permission	Can I open the window?
may	to express possibility	I may be home late.
may	to request permission	May I sit down, please?
must	to express obligation	I must go now.
must	to express strong belief	She must be over 90 years old.
should	to give advice	You should stop smoking.
would	to request or offer	Would you like a cup of tea?
would	in if-sentences	If I were you, I would say sorry.

Modal verbs are unlike other verbs. They do not change their form (spelling) and they have no infinitive or participle (past/present). The modals must and can need substitute verbs to express obligation or ability in the different tenses. Here are some examples:

Past simple	Sorry I'm late. I had to finish my math test.
Present perfect	She's had to return to Korea at short notice.
Future	You'll have to work hard if you want to pass the exams.
Infinitive	I don't want to have to go.

Past simple	I couldn't/wasn't able to walk until I was 3 years old.
Present perfect	I haven't been able to solve this problem. Can you help?
Future	I'm not sure if I will be able to come to your party.
Infinitive	I would love to be able to play the piano.

Modals are auxiliary verbs. They do not need an additional auxiliary in negatives or questions. For example: Must I come? (Do I must come?), or: He shouldn't smoke (He doesn't should smoke).

 

A Few Basic Grammatical Rules Applying to Modal Verbs

• Modal verbs are NEVER used with other auxiliary verbs such as do, does, did etc. The negative is formed simply by adding "not" after the verb; questions are formed by inversion of the verb and subject:

You should not do that.
Could you pick me up when I've finished?

• Modal verbs NEVER change form: you can never add an "-s" or "-ed", for example.
• Modal verbs are NEVER followed by to, with the exception of ought to.

Uses of Shall, Will and Should

In England, shall is used to express the simple future for first person I and we, as in "Shall we meet by the river?" Will would be used in the simple future for all other persons. Using will in the first person would express determination on the part of the speaker, as in "We will finish this project by tonight, by golly!" Using shall in second and third persons would indicate some kind of promise about the subject, as in "This shall be revealed to you in good time." This usage is certainly acceptable in the U.S., although shall is used far less frequently. The distinction between the two is often obscured by the contraction 'll, which is the same for both verbs.

In the United States, we seldom use shall for anything other than polite questions (suggesting an element of permission) in the first-person:

• "Shall we go now?"
• "Shall I call a doctor for you?"

(In the second sentence, many writers would use should instead, although should is somewhat more tentative than shall.) In the U.S., to express the future tense, the verb will is used in all other cases.

Shall is often used in formal situations (legal or legalistic documents, minutes to meetings, etc.) to express obligation, even with third-person and second-person constructions:

• The board of directors shall be responsible for payment to stockholders.
• The college president shall report financial shortfalls to the executive director each semester."

Should is usually replaced, nowadays, by would. It is still used, however, to mean "ought to" as in

• You really shouldn't do that.
• If you think that was amazing, you should have seen it last night.

In British English and very formal American English, one is apt to hear or read should with the first-person pronouns in expressions of liking such as "I should prefer iced tea" and in tentative expressions of opinion such as

• I should imagine they'll vote Conservative.
• I should have thought so.

Uses of Can and Could

The modal auxiliary can is used

• to express ability (in the sense of being able to do something or knowing how to do something):
  He can speak Spanish but he can't write it very well.
• to expression permission (in the sense of being allowed or permitted to do something):
  Can I talk to my friends in the library waiting room? (Note that can is less formal than may. Also, some writers will object to the use of can in this context.)
• to express theoretical possibility:
  American automobile makers can make better cars if they think there's a profit in it.

The modal auxiliary could is used

• to express an ability in the past:
  I could always beat you at tennis when we were kids.
• to express past or future permission:
  Could I bury my cat in your back yard?
• to express present possibility:
  We could always spend the afternoon just sitting around talking.
• to express possibility or ability in contingent circumstances:
  If he studied harder, he could pass this course.

In expressing ability, can and could frequently also imply willingness: Can you help me with my homework?

Uses of May and Might

Two of the more troublesome modal auxiliaries are may and might. When used in the context of granting or seeking permission, might is the past tense of may. Might is considerably more tentative than may.

• May I leave class early?
• If I've finished all my work and I'm really quiet, might I leave early?

In the context of expressing possibility, may and might are interchangeable present and future forms and might + have + past participle is the past form:

• She might be my advisor next semester.
• She may be my advisor next semester.
• She might have advised me not to take biology.

Avoid confusing the sense of possibility in may with the implication of might, that a hypothetical situation has not in fact occurred. For instance, let's say there's been a helicopter crash at the airport. In his initial report, before all the facts are gathered, a newscaster could say that the pilot "may have been injured." After we discover that the pilot is in fact all right, the newscaster can now say that the pilot "might have been injured" because it is a hypothetical situation that has not occurred. Another example: a body had been identified after much work by a detective. It was reported that "without this painstaking work, the body may have remained unidentified." Since the body was, in fact, identified, might is clearly called for.

Uses of Will and Would

In certain contexts, will and would are virtually interchangeable, but there are differences. Notice that the contracted form 'll is very frequently used for will.

Will can be used to express willingness:

• I'll wash the dishes if you dry.
• We're going to the movies. Will you join us?

It can also express intention (especially in the first person):

• I'll do my exercises later on.

and prediction:

• specific: The meeting will be over soon.
• timeless: Humidity will ruin my hairdo.
• habitual: The river will overflow its banks every spring.

Would can also be used to express willingness:

• Would you please take off your hat?

It can also express insistence (rather rare, and with a strong stress on the word "would"):

• Now you've ruined everything. You would act that way.

and characteristic activity:

• customary: After work, he would walk to his home in West Hartford.
• typical (casual): She would cause the whole family to be late, every time.

In a main clause, would can express a hypothetical meaning:

• My cocker spaniel would weigh a ton if I let her eat what she wants.

Finally, would can express a sense of probability:

• I hear a whistle. That would be the five o'clock train.

Uses of Must

Examples here refer to British English; there is some variation in American English.

Necessity and obligation

Must is often used to indicate 'personal' obligation; what you think you yourself or other people/things must do. If the obligation comes from outside (eg a rule or law), then have to is often (but not always) preferred:

•  I really must get some exercise.
• People must try to be more tolerant of each other.
• You musn't look - promise?
• If you own a car, you have to pay an annual road tax.

Strong advice and invitations

• You must go and see the film - it's brilliant.
•  I think you really must make more of an effort.
• You must come and see me next time you're in town.

Saying you think something is certain

• This must be the place - there's a white car parked outside.
• You must be mad.
• What a suntan! You must have had great weather.

The negative is expressed by can't:

• You're going to sell your guitar! You can't be serious!
• She didn't wave - she can't have seen me.

Uses of Ought to

Ought to usually has the same meaning as should, particularly in affirmative statements in the present:

• You should/ought to get your hair cut.

Should is much more common (and easier to say!), so if you're not sure, use should.

References:

http://esl.fis.edu/grammar/rules/modal.htm.

http://grammar.ccc.commnet.edu/grammar/auxiliary.htm.

http://library.bcu.ac.uk/learner/Grammar%20Guides/3.07%20Modals.htm