The major defining feature of metals is that electrons flow relatively freely between atoms in any object composed of two or more metal atoms, whereas electrons around nonmetals are more tightly bound to their respective nuclei or within individual chemical bonds. This results in other significant features of metal, particularly their high thermal and electrical conductivity. A large majority of known elements are metals.
Metals have several other common features that distinguish them from nonmetals, but few are universal. Almost all metals are solid at room temperature, but a large number of nonmetals are gaseous. Pure metals tend to have a shine or luster, but nonmetals tend to be dull in appearance. They tend to have relatively high densities. They also tend to be malleable and ductile, which means that they can be hammered and drawn into wires. However, solid nonmetals tend to be hard and brittle.
Metals lose electrons easily, and they often corrode easily. The oxides of metals tend to be basic, but the oxides of nonmetals tend to be acidic. Unlike electricity and heat, nonmetals conduct light better than metals, and thin sheets of metal are usually opaque while thin sheets of nonmetals are usually translucent or even transparent.