screws nuts and bolts

I never thought of using a microwave carcass for nuts and bolts and misc small pieces.

Might have to put a piece of ducktape over the small holes if you break it all the way down.

I know someone who even stuffs appliances with glass.

That's not even right, they'll be the first one to bi**h when the yard screws them.
Ferrite into the steel buckets is not cheating on your load, there is magnetized and non magnetized ferrite available. Also there is lots of ferrite on circuit boards and some transformers.

I take #10 food cans and fill them up with the small bits then toss it in with a load. If it's steel, it goes in there. Dryer drums are good for this too. I even throw the caps from the beer I drink in there.