All electric guitars' pickups have wires connecting them to knobs (pots), switches, and input jacks. Your guitar's pickups require a steady stream of electricity in order to work. Have you ever heard your guitar crackle when you turned one of the knobs? Has your guitar ever lost a its signal when you bumped a knob or input jack? These problems are usually caused by broken solder connections. All of the wires connecting your electrical components are soldered together in some way. The soldered joint creates a strong bond between the wires and the components to insure a steady stream of electricity. Unfortunately, some times solder joints can break. That is where a soldering gun comes into play.
Soldering guns or pencils take the electricity from the wall outlet and run it through a metal tip. The metal tip heats up because of the electricity. This hot metal tip is then used to warm up the metal wires and electronic components. After the components are warm, you can apply solder to the wire and component. In a split second, the solder melts, solidifies, and creates a metal solder joint that secures your wires in place. Broken solder joints are very common in all electric guitars. After years of use and abuse, solder joints and crack and break off. This is an easy fix as long as you have your soldering gun.
Soldering guns can also be used for other guitar repair other than electronic repairs. A soldering gun is often used to remove guitar frets. The warm solder tip helps heat up the glue that holds the fret in place. Once the glue is loose, the fret can easily be pulled out of the fretboard. The soldering gun not only helps loosen the fret, it also saves the fretboard. If you tried to pry a fret out of the fretboard without loosening the glue, chances are you would take a big chip out of the fretboard.
Soldering guns have many uses. Mainly they are used to solder electronic parts and wiring. Up until recently, all guitars had solder joints. This means that you will have plenty of people coming to you asking if you can fix their guitar electronics. I strongly advise getting a soldering pencil. You don't need to get a full blown soldering gun, but you should at least have a pencil. You can do all the electronic repairs you want with one of these. If you would like more information about soldering guitar electronics, please see my guitar electronic soldering article.