Ok my research indicates the silver square is called the waveguide cover. So wondering if replacing it will make the microwave usable

There are several similar videos. I didn't bother checking all of them.
Was there something being cooked that could have spattered in the microwave when the window (waveguide cover) failed?
Remove the window as shown in the video. put a small shallow bowl of cold water in the micro wave. Run the microwave for 10 or fifteen seconds and watch for sparks. No sparks? Shut it off and remove input power or disable it from being used. Look up the part number if your manual lists it and order a replacement window (waveguide cover).
DO NOT USE A MICROWAVE WITH A DEFECTIVE WINDOW OR WITHOUT ANY WINDOW. Even just heating water could wreck it.
If it sparks with the window removed, shut off immediately. Don't turn it on again. Get it serviced or replace it.
Good luck.

Here is a link that might be useful: Youtube is your friend

This post was edited by laat2 on Wed, Nov 19, 14 at 14:56

Thanks for posting that video. I was able to go to a parts store and they cut me a new waveguide. So far so good, no sparks!

Excellent outcome!
(That would be a waveguide cover.)