“Cold-welding” is a process for sticking two metals together with no heat
It turns out there are more ways to stick two pieces of metal together other than melting them. A common process in space is “cold” or “contact” welding, where two parts can join without any heat or fusing. The vacuum can bring flat surfaces of similar metals to join together.
This method of welding is also used here on Earth in specific contexts. For example, it is common to use this process to joint copper wires and get a more durable joint. It is also used to weld together nanowires, which can be done easily by mechanical contact and applying relatively low pressure.