Uses:

‘will/shall + infinitive’

• We use the future simple to express a promise.

They will allow you to go through.

He shall be present tomorrow at the meeting.

I will do my best.

• We use the future simple to express a prediction about the future.

His birthday will bring much happiness to the people.

Next year will be a great surprise.

I don’t know what will happen if doesn’t succeed.

• We use the future simple to express a voluntary action, usually it is used for a spontaneous decision right in the moment as we’re making it.

Can you help me please? Yes, I will help you right this instant.

Could you send me the check please? Yes, I will send send it now.

He shall prepare your lunch sir.

He will make the order.

Note: There are many similarites between ‘will’ and the ‘be going to’ form. For instance both can mean ‘an intention’, or ‘a prediction’. 

An intention:

‘I am going on vacation in March’. or ‘I will go on vacation in March’.

A Prediction:

‘I think this man is going to be the next president’. or ‘I think this man will be the next president’.