SO2 (sulfur dioxide) is not a metal. It is a compound made up of two nonmetals: sulfur (S) and oxygen (O).

Here's why:

* Metals tend to lose electrons and form positive ions (cations).

* Nonmetals tend to gain electrons and form negative ions (anions).

In SO2, sulfur and oxygen share electrons in covalent bonds, forming a molecule rather than ionic compounds like those formed by metals.