A soldering iron is a device that melts solder through a small heated metal tip. It is used for joining electrical components together, such as wires to a motor. Soldering irons can be heated by electricity or by burning a fuel such as butane.

Cleanliness is important when operating a soldering iron. If the tip becomes dirty, usually with burned soldering flux, heat transfer is reduced. In order to work properly, the tip must be cleaned occasionally during operation by drawing it along a damp sponge or rag. A small amount of solder is then melted on the tip to aid in heat transfer. This procedure is called tinning. The tip is then placed against the work in order to heat it to a temperature sufficient to melt the solder and allow it to flow over the work. Soldering irons are never used to trowel molten solder over the work.