I have a hot water heater & the pipes in my wall bang crazily whenever the heat starts or stops. We can't have the heat on at night because it is so loud. Even now at night with the heat turned right down... there is still banging in the wall. It is honestly really loud and I don't know what to do.

Jodi::(

Bleed radiators to eliminate air that causes banging.
Make sure the fill valve is set to the proper altitude for the system.
Secure and drain expansion tank just in case it is water logged.
Make sure the circulating pump is operating properly.

The above items shold take care of your situation.
If necessary you might have to call a professional to address the above items unless you know how to do them.

I would also venture a possible problem being that you have zone valves and they are slamming shut at the end of a call for heat, and it could also be air in the system...