Taillight wiring Help Needed

[MikeyMan]

The metal tail light housing should be bolted or screwed to the fender or bumper. If everything is metal to metal, it should be fine. Sometimes if there's a lot of rust you won't make good contact. The whole metal truck body is the "ground" or negative "-" part of your electrical connection. Your wires provide the power or positive "+" to the lights, and the metal body is the "-" ground that completes the electric connection.