I always think about ElectroBoom purposely trying to make a microwave fail catastrophically with metal objects in it, and what he found was that unless it had some kind of jagged edge or narrow points (like a cut up can or a fork as opposed to an unopened can or a spoon), nothing happened.

Balling up tinfoil barely did anything. A fork would cause sparks off the ends of the tines. I think he eventually got a fire started in there but it took effort to make it happen.

Meanwhile, I put a whole potato in mine not even covered in foil and that fucker sparks and catches fire like a mofo.