FUTURE TENSE

The most common auxiliary verbs used to express futurity are will and shall.
Prescriptive grammarians distinguish between these, preferring to express the simple future as will in the second and third persons and shall in the first person, and preferring to express obligation or determination in the opposite cases. However, in modern English worldwide, shall and will are generally used interchangeably,^[4] with will being more common. See also shall and will.
Other periphrastic forms for the future include:

• to be going to + Verb, e.g. John is going to leave tonight.
• to be to + Verb, e.g. John is to leave tonight, which with the zero copula of newspaper headline style becomes simply to + Verb, e.g. John to leave tonight.

A periphrastic form for the immediate future is

• to be about to + Verb, e.g. John is about to leave (any minute).

A dialectical form in Northern England is:

• mun, derived from Old Norse, which implies obligation.

In all dialects of spoken English both shall and will are commonly elided into 'll (I'll go could be either "I will go" or "I shall go") so that the differences between the two have been worn down.
English also uses must, should, can, may and might in a similar way:

• Must expresses the highest degree of obligation and commitment (I / you must go) and is temporally nearest to present time in its expression of futurity ("I must go now.")
• Should (the subjunctive form of shall in this context) implies obligation or commitment to the action contemplated.
• Can implies the ability to commit the action but does not presuppose obligation or firm commitment to the action.
• May expresses a relatively low sense of commitment (I may go) and is the most permissive (You may go); it can also suggest conditionality (I may go [if I have time]).
• Might expresses a very low sense of commitment or obligation (I / you might go if I / you feel like it).

English often employs the simple non-past (base form or base form + s in the third person singular) to convey scheduled futurity, as in tomorrow I leave at 5:00.
The simple non-past form is mandatory for expressing the future in a dependent clause when the main clause uses will, shall, or (be) going to: I will see you when I get there (not ...when I will get there); If you build it they will come (not If you will build it...); she will not know that I am there (not ...that I will be there).

Summary of forms

• I will/shall go
• I'm going to go / I am going to go
• I'm to go / I am to go
• I'm about to go / I am about to go
• I must go
• I should go
• I can go
• I may go
• I might go
• I go

To express futurity in the negative, a negative adverb such as not or never is inserted before the main verb (or the suffix -n't is added to the auxiliary), as in all other auxiliary constructions:

• I will/shall not go.....I won't/shan't go.....Will/shall I not go?.....Won't/shan't I go?
• He's not going to go / He is not going to go.....Is he not going to go?.....Isn't he going to go?
• He's not to go / He is not to go.....Is he not to go?.....Isn't he to go?
• He's not about to go / He is not about to go.....Is he not about to go?.....Isn't he about to go?
• I must not go.....I mustn't go.....Must I not go?.....Mustn't I go?
• I should not go.....I shouldn't go.....Should I not go?.....Shouldn't I go?
• I cannot go (cannot is conventional rather than can not).....I can't go.....Can I not go?.....Can't I go?
• He may never go.....May he never go?
• I might not go.....I mightn't go.....Might I not go?.....Mightn't I go?

In all of these, action within a future range of time is contemplated. However, in all cases, the sentences are actually voiced in the present tense, since there is no proper future tense in English. It is the implication of futurity that makes these present tense auxiliary constructions amount to a compound future quasi-tense.