 Like spot welding , seam welding relies on two electrodes to apply pressure and current to join metal sheets . However , instead of pointed electrodes , wheel @-@ shaped electrodes roll along and often feed the workpiece , making it possible to make long continuous welds . In the past , this process was used in the manufacture of beverage cans , but now its uses are more limited . Other resistance welding methods include butt welding , flash welding , projection welding , and upset welding . 
