What's the difference: "I am to go" and "I have to go"

[Lujdmila]

Hello! Are there any differences between two sentences: "I am to go" and "I have to go".
One person said me that if we use "I am to go" it means that only I must go. So this variant we use if we have debate.
So when we use "I have to go" it means just a fact: I need to go.

Is it correctly or not?

 

[riquecohen]

Welcome to the forum, Lujdmila.

"I am to ..." is used to refer to a plan that has been made for the future.
Examples:
I am to go to the show next week.
He is to contact me as soon as he arrives in town.
They are to sing at two concerts during the tour.

You are correct about "I have to go." It can mean "I need to go" or "I must go."