Why do materials absorb some frequencies of electromagnetic radiation and not others

Most metals have a specific build of electrons that makes them produce electricity better while other objects like plastic does not have electrons. Pretty much electrons are the things that help objects produce electricity well.

I dont know but i think it is 

the problem with quantum mechanics is that there is no way to verify its claims.

Aform of energy that is reflected or emitted from objects in the form of electrical and magnetic waves that can travel through space. there are many forms of  electromagnetic  energy including gamma rays, x rays, ultraviolet radiation, visible light, infrared radiation, microwaves and radio waves.