* Physical Properties: Sulfur is a brittle yellow solid at room temperature. Metals are generally shiny, malleable, and ductile.

* Electrical Conductivity: Sulfur is a poor conductor of electricity. Metals are excellent conductors.

* Chemical Properties: Sulfur readily forms covalent bonds with other nonmetals, a characteristic of nonmetals. Metals tend to lose electrons and form ionic bonds.

In summary, sulfur lacks the key properties that define metals, making it a nonmetal.