The main difference between metal and plastic electrical boxes

Feature Metal Electrical Boxes Plastic Electrical Boxes Material Steel or aluminum PVC or fiberglass Grounding Must be grounded because metal conducts electricity No grounding needed since plastic is non-conductive Durability Stronger and more resistant to impact Can crack or break if overtightened or hit Cost Usually more expensive Usually cheaper Ease of Installation Harder to cut and install Lighter and easier to work with Cable Compatibility Best with metal conduit or armored cable (BX/MC)Best with non-metallic cable (Romex/NM)Fire Resistance Better fire resistance Lower heat tolerance (but still code-approved)

When to Use Metal Boxes

• With metal conduit systems

• In commercial buildings

• Where extra strength or protection is needed

• When using armored cable (MC/BX)

When to Use Plastic Boxes

• In most modern residential wiring

• With NM (Romex) cable

• When you want faster, easier installation

Simple Rule of Thumb

• Metal conduit → Metal box

• Romex (NM cable) → Plastic box

✔ Both types are code-approved when used correctly.

If you want, I can also explain:

• Why electricians sometimes still prefer metal boxes

• When plastic boxes are not allowed by code

• Common mistakes people make when choosing boxes.