Originally Posted by mariashamshad

In assertive sentences merely future time is denoted by " shall" in first person and " will " in the second and third person.
Thus we should say
I shall read.
He will reAd.
You will read.
We shall read.
When however a " command" or " promise" or " intention" is to be expressed the " shall" is used with the second and third persons.
Shall is used with the second and third persons to combine future time with an implied command.like,
He shall go( i command you to go).
If you do this, you shall be hanged( threat).