Fuses are devices used in electrical circuits to protect against overcurrent conditions. A fuse is a metal wire element with a very low resistance. This wire melts whenever a current higher than the rating of the wire flows through it.  The overcurrent condition can damage the circuit and may lead to fires or explosions.  Overcurrent conditions can be caused by short circuits, meaning the connected load is drawing more current from the source, which will result in device failure.

The fuses can be either slow blow or fast blow, depending on the time taken by the fuse to safely activate and disconnect the circuit. Self-resetting fuses automatically restore the circuit after the overload condition is cleared.

The fuse element is made of zinc, copper, silver or aluminium. The fuse bodies can be made of metal, ceramic, glass or fiberglass depending on the application. Fuses can be soldered directly on the printed circuit board or mounted in the fuse holders that are soldered to the board. This helps with the easy replacement of the fuse in case any damage occurs on the circuit board.

A fuse has ratings that indicate the maximum current that can flow through it, the applied voltage, the response speed and the maximum current.

Fuses are available in a vast array of sizes and serve in many applications. For example, automotive specific fuses are used to protect the electrical equipment in an automobile while high voltage fuses are used to protect electricity metering transformers.