Grounding Points

Almost everything that is powered electrically in your car is grounded to the frame or the body of the car. These are called "grounding points" and serve to complete the power loop for sending electricity around within the car. Example: current from the positive wiring from the positive terminal of the battery, or fuse box, travels to a light bulb. Once the current has passed through the filament of the light bulb, it passes through the housing of the light bulb and grounds to the frame. The negative battery terminal is also grounded to the frame, which causes the frame to serve as a gigantic piece of wire.