If you were to peel back the layers of time and look at how people welded in the olden days, the first thing that you would notice is that they used fire. There is a pretty good chance that fire is almost never used in welding as it is done in this modern day and age. This is because of the fact that it is difficult to control, and you need a very consistent level of heat if you want the welding to be done in a way that looks absolutely clean and professional without anyone being able to argue against that being the case.
Heat can be generated in lots of ways. Electricity is often used because of the nature of its function. Running a current through a wire would likely not generate any heat, but introducing the tiniest bit of resistance into the current will cause heat to start accumulating. This would obviously not be ideal in situations where you want to power your home, but the fact of the matter is that it is highly desirable if resistance welding is what you are attempting to learn a thing or two about.
Generating electrical resistance can cause fires, but if the heating element is strong enough to take the heat then it can be used to melt metal for welding purposes. This is just one of the numerous welding methodologies that are being implemented in countless industrial settings, and it is great for experienced professionals who want to start taking their skills to the next level. Knowing how to resistance weld can help you get even better jobs which would enable you to live a much better type of lifestyle too.