The future simple, or the future indefinite, is the most common way to speak about the future. We use the future simple when it is not necessary to stress the length and the result of the action.
However, the verb "will" has more functions than just referring to the future on a timescale. It is closely related to the nouns "will", "willingness" and it often has the same shade of meaning.
Facts and predictions
Using the future simple, we can speak about things which are certain and make predictions when we are not 100% sure that something will happen.
The shop opens at 9 a.m. So, at 8 a.m. it will be closed.
The conference will take place in Berlin.
Who do you think will win the championship?
I don't think this plan will work.
Using the future simple, we can offer to do something or ask somebody to do something for us. The negative form will have the opposite meaning: we use "won't + verb" when we don't want to do something or refuse an offer.
Will you help me carry the bags? = Do you mind carrying the bags for me?
Will you wait for me, please? I'll be back in a minute. = Could you wait for me?
I will call them, it's not a problem at all. = I don't mind calling them.
I won't do that! Don't ask me to! = I don't want to do that.
We can use won't + verb in the meaning of unwillingness not only in relation to people but to things as well.
The car won't start. = It "doesn't want" to start.
I'm trying to unlock the door, but it won't open. = It "doesn't want" to open.
Decisions on the spot
We use the future simple when we make a decision right now, on the spot. We didn't plan it before.
A: I'm thirsty. B: I'll give you some water.
A: Have you received an email from me? B: Just a second, I'll check my email box.
Questions-offers with shall I / shall we
We are asking what you think about something. Are you for or against? Remember that we can only use shall with "I" and "we".
Shall I close the window? = Is it alright if I close the window?
Shall we go for walk? = What do you think about going for walk now?
Shall I call you at eight? = Do you mind if I call you at eight?
The first conditionals
We also use the future simple in conditional sentences of the first type.
If I go to Paris, I will visit the Louvre.
If there aren't any non-stop flights, I'll book a flight with stopovers.