Molecular compounds are composed of nonmetals. They are formed by the chemical bonding of two or more nonmetallic elements. Examples of molecular compounds include water (H2O), carbon dioxide (CO2), and methane (CH4). In contrast, metallic compounds are formed by the chemical bonding of a metal and one or more nonmetals. Examples of metallic compounds include sodium chloride (NaCl), copper sulfate (CuSO4), and iron oxide (Fe2O3).