Resistance welding machines are devices used to join metal parts by resistance welding. Resistance welding is a welding process in which electric current is passed through the metal parts to be welded, generating heat. The heat melts the metal at the point of contact and creates a joint. Resistance welders are widely used in industry to join metal parts together quickly and effectively. They can be used to weld parts in the automotive, shipbuilding, aerospace, and many other industries. There are several types of resistance welding machines, including spot welding machines, butt welding machines, and roller seam welding machines. Each type of resistance welding machine has its own specific applications and advantages, but all are based on the same basic principle of passing current through metal parts to make a welded joint.