system
Given the following post, respond as if you're commenting on Reddit:
human
Eli5. Cold welding. Im a highschool student and ive got welding experience but i just don’t understand how cold welding works like in space and even on earth. What exactly constitutes a cold weld and how is it achieved? (Unintentionally)
gpt
Metal atoms really like to stick to each other. That's why metals are both flexible and strong.

However, when metal atoms touch oxygen or water, they react easily to form an oxide. The surface of metal exposed to air is coated with the oxide which slows down metal atoms inside from reacting. Rust is one example of iron oxide.

Cold welding occurs in an environment without anything in the air for the metal to react and form an oxide. Space is one such environment. When bare metal atoms touch other atoms in a cold weld, they stick together much like two water droplets fusing into one. For metal the cold weld causes two solids to combine into one larger one.