What determines if an element is a metal?

Elements that are metals tend to be good conductors of heat and electricity, highly reactive, malleable, ductile, shiny, opaque and solid at room temperature. However, individual metals vary in how well they match this description. Mercury is a liquid at room temperature, while gold is rather nonreactive.

The elemental metals appear in a large group on the periodic table, and they make up a large majority of the elements. Metals dominate the lower-left side of the periodic table, and many tables have markings separating the metals from nonmetals. Approximately 75 percent of the elements are metals, and all the gaseous elements are nonmetals.