Microwaves can pass through glass and plastic, but they can’t pass through metal.
Strangely, they also can’t get through a hole that’s significantly smaller than their wavelength, so the fine metal mesh keeps them inside the oven, while letting some light out.
In other words, your microwave oven is safe and your brain won’t fry if you put your head too close to the glass door. Besides, microwaves are just radio waves, and definitely not radiation like most of use assume.
