Why are metals generally good conductors of electricity?

In solid materials, electric current is carried by the flow of electrons. Metals are excellent conductors because their atomic structure allows their outermost electrons to detach easily and move freely from atom to atom, forming a conductive 'sea of electrons.' Protons are tightly bound in the nucleus of an atom and do not flow to create electrical current in solid conductors, making 'many free protons' completely incorrect. Density has no direct correlation with conductivity, as many heavy, dense metals are far worse conductors than much lighter ones.