system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why does metal heat up so much when crushed under a hydraulic press?
gpt
Almost every metal is made up of crystals - ordered arrangements of atoms. Some metals are made of very small crystals, some are made of large crystals, and some very special metal parts can be made of a single crystal.  These crystals aren't perfect - they have little atom-sized holes in them, and atoms stuck where they aren't supposed to be.

When you permanently change the shape of a piece of metal, the way it actually changes shape at an atomic level is that the holes and the misplaced atoms are forced to move around. A huge number of these holes and misplaced atoms moving around makes up the change in shape you see.  But just like almost everything else, when you move these holes around, they are opposed by friction.  Most of the work you put into changing the shape of the metal doesn't actually change its shape - instead, it's used to move against friction, and is wasted.  That work gets converted into heat.