When we ask someone to do something, we can use Future Simple in the form of a question. Normally, we use pronoun YOU in this situation. Invitation is a form of asking too.
Will you marry me? (I am asking you to marry me)
When we ask someone to do something in the form of invitation:
Will you please come with us? (I am asking you to come with us)
However, we have other uses of Future Simple Tense: