When an applied electric field is applied to a metal, the electrons in the guide band are leaped inward at a higher energy level, and the movement is generated through the lattice along the direction of the applied electric field, which illustrates the conductivity of the metal. The electrons in the band can absorb light energy, and they can also emit the absorbed energy, which shows that the luster of the metal and the metal is an excellent reflector of radiant energy. Electrons can also transmit heat energy, indicating that the metal has thermal conductivity. When stress is applied to a metal crystal, since the electrons in the metal are off-domain (that is, not belonging to any one atom and belong to the metal as a whole), the metal bond of one place is destroyed and a metal bond can be formed in another place, so the machining does not destroy the metal structure, but only changes the shape of the metal The cause of common mechanical processing properties such as plasticity.

The more unpaired electrons a metal atom provides for the formation of an energy band, the stronger the metal bond, the higher the melting point and boiling point of the reaction in physical properties, and the greater the density and hardness. The theory of energy band is difficult to explain some problems, such as the high hardness, high melting point and other properties of some transition metals, some people think that the sub-outer electrons of atoms participate in the formation of partial covalent metal bonds. Therefore, the theory of metal bond is still developing.