What is the difference between an ionic lattice and a metallic lattice?

Many elements readily form ions because their electron configurations are more stable if electrons are added or removed, usually in order to ensure that the outermost shell is a full octet. An ionic compound consists of cations and anions in a lattice structure. The most common example of such a compound is NaCl, which consists of Na⁺ cations and Cl^- anions. The ionic lattice structure is held together by the electrostatic forces of attraction between the oppositely charged ions. A metal or metal alloy consists of metal cations and a sea of delocalised electrons. For example a metal atom M may have two electrons in its outer shell, in which case in order to obey the octet rule two electrons will dissociate to form an M²⁺ ion. In this case the metallic structure will be held together by the attraction between the M²⁺ ions and the delocalised electrons. In general, the metallic lattice structure is held together by the electrostatic forces of attraction between the metal cations and the delocalised electrons.