Adding to James' answer: All his examples describe something that is about to happen or may happen. And "am to" for 1st person singular (I), "is to" for 3rd person of singular (he/she/it)

Hello, Zerious: Do you have a copy of Michael Swan's PRACTICAL ENGLISH USAGE? He explains it fully. Here are some of his examples: 1. To talk about plans in a FORMAL style: The President is to visit Nigeria next month. 2. To talk about things that were fated: I thought that we were saying goodbye forever. But we were fated to meet again. 3. With -if clauses: If we are to get there by lunchtime, we had better hurry. 4. Orders: You are to do your homework before you watch TV. 5. Instructions: This cover is not to be removed.

"to be to" -- intention, obligation you are to open this box in 10 seconds = you should open this box in 10 seconds