Metallic bonding is the force of attraction between valence electrons and the metal ions. Molecules within metals called "alkali reactive force". It is the sharing of many detached electrons between many positive ions, where the electrons act as a "glue" giving the substance a definite structure. Metals form giant structures in which electrons in the outer shells of the metal atoms are free to move. The metallic bond is the force of attraction between these free electrons and metal ions. Metallic bonds are strong, so metals can maintain a regular structure and usually have high melting and boiling points. An alloy is a mixture of metals or a mixture of a metal and another element.