Metallic bonding allows metals to have unique properties. Metals form a regular lattice structure where the outer electrons separate from the metal atoms to form a "sea of electrons". This delocalizes the electrons and allows them to move freely through the metal. The metal atoms become positively charged ions that are attracted to the sea of electrons, called metallic bonding. This strong bonding allows metals to conduct heat and electricity well and be hard and malleable. Band theory can explain these properties by describing the states that form from the overlapping atomic orbitals in a metal lattice.