While it can form different structures and compounds, carbon itself is classified as a nonmetal.

Here's why:

* Lack of metallic properties: Carbon doesn't conduct electricity or heat well, and it isn't malleable or ductile.

* Formation of covalent bonds: Carbon primarily forms covalent bonds with other elements, unlike metals which typically form metallic bonds.

* Presence in organic compounds: Carbon is the backbone of all organic molecules, making it a defining element of life.

Although carbon can form materials with very different properties like diamond (hardest natural substance) and graphite (a soft lubricant), the element itself is classified as a nonmetal.