Why does the microwave oven make a snapping sound when it is heated?

There is metal in it. The principle of microwave oven is that the wavelength of microwave is close to particles, which causes particles to vibrate and generate heat energy. The heat energy of metallic substances is transferred quickly. If you put a metal substance into a microwave oven, it will cause instant energy to be released into the air. This phenomenon of releasing a lot of energy instantly is the form of explosion, which will cause harm to the surrounding objects. So don't put metal into the microwave oven for operation.