My microwave trips the 20 amp breaker so I go down stairs and trip the breaker and it instantly trips again... the microwave is on its own 12-2 20amp breaker as I even changed the breaker with a new 20 amp breaker and still does the same thing.When I unplug the microwave and trip the breaker the breaker doesn't trip so I know the wiring is correct and not touching any metal but I don't know what else to do to get my microwave working

It seems kind of obvious, but have you tried the microwave on another circuit?

When I had this problem the answer was a problem in the wall plug.

Yes I did and it still trips that breaker also

There are two electricians around - hopefully one shows up.

I'd be afraid my house is going to burn down every time I use the microwave!

A microwave uses a lot of power. If you are tripping breakers, you have an issue with the unit, probably in the magnetron, the radiation generator. They are not worth repairing unless under warranty. I recently had a MW repaired under warranty and they charged Kitchen Aide more then I paid tor the unit. I will assume this is an on counter MW. HD, Lowe's and HH Gregg sell units for $100-150 that would be cheaper then repair.

You can take it apart and check the magnetron for a dead short and look around until you can find the part or wire that's shorting out. The magnetron has an overload in it that should trip and prevent it from tripping a breaker. More than likely, what you have is a loose wire somewhere touching the cabinet. First, take your ohm meter and read from the hot prong (The small one that goes on right-hand side of receptacle.) to ground. If it reads zero you have a dead short to the cabinet. It could be a very simple and easy fix, you will never know until you try. Learn to use a meter and track down problems. It's fun to fix your own equipment. Look at these: https://dl.dropboxusercontent.com/u/8010163/How%20to%20use%20Test%20Equipment%20Service%20Manu al.pdf
https://dl.dropboxusercontent.com/u/8010163/How%20to%20Diagnose%20and%20Fix%20Everything%20Ele ctronic.pdf