In-game description:

"Solid. Conducts Electricity. Meltable."

Reactions

Metal reacts with SPRK, that can form an electricity path. Other ways Metal can do this, is when it comes into contact with BTRY, THDR, ELEC, LIGH, or other metals that have "passed on" the SPRK. Metal can also conduct heat.

Uses

Good for many electronics, circuits, switches, batteries, et cetera. It can be used like copper is used.