Recently I came across with one video in youtube where the guy in the video did experiment on microwave oven. He heat up aluminium foil in the oven and after a few second, the foil started to produce spark. This is my first time watching something like that. I never knew that when metal is heat up in microwave oven, it will produce spark. I have read several website which explain about this, but I just could not understand them. So, I really appreciate if someone could explain to me in the simplest way..