Materials: Usually steel, stainless steel, or aluminum. Excellent durability and mechanical strength. Fire-resistant and safe for high-heat environments. This guide explains junction box types by use, material, shape, installation method, and environment, while highlighting safety codes and selection considerations. Junction boxes are typically made of metal or plastic. What Does A Junction Box Do? A junction box serves a variety of purposes: In short: junction boxes serve as a protective casing for a.