Here's why:

* Physical Properties: Sulfur is a brittle, yellow solid at room temperature. It's a poor conductor of heat and electricity.

* Chemical Properties: Sulfur readily forms compounds by gaining electrons (acting as a nonmetal). It typically has a negative oxidation state in its compounds.

* Location on the Periodic Table: Sulfur is located in Group 16 (VIA) of the periodic table, which contains the nonmetals oxygen, selenium, tellurium, and polonium.

While sulfur can exhibit some metallic properties in certain forms, it's primarily classified as a nonmetal based on its overall characteristics.