Metals conduct electricity well because their electrons can move more freely than those in nonmetals. The structure of a metal atom's electron cloud makes it easy for the atom to gain or lose electrons in chemical reactions. Electrons repel these loose electrons and send them through the metal.
Electrons carry a negative charge and therefore repel one another. When a current is introduced, it creates a chain reaction of electrons being ripped from the outer shell of each atom. This outer shell, known as the valence shell, controls how the atom behaves, and whether it will have an ionic or covalent chemical reaction. The atom naturally is inclined to have a full shell and will gain or lose electrons as needed. Also, metals have densely packed molecules, making their atoms and electrons more likely to interact without energy loss. The same traits that allow metals to conduct electricity also allow them to conduct heat. Copper, silver and gold conduct heat and electricity the most efficiently. Although silver has a higher conductivity, copper gets more use because it is cheaper and more widely available. Metal conducts electricity better in extreme cold because the lack of molecular collisions lets electrons move forward more easily.