Iron golems rust in multiple stages, like iron items, rather than all at once. Each stage cuts its maximum HP by 20 (so a rusty golem has 60 max HP, etc.) Applying a can of grease will remove the rust and restore its max HP to normal, and may prevent further water damage for a little while. The golem may also quaff a potion of oil, which has a similar effect, except it also restores current HP as well as maximum by the amount of erosion removed.

Iron golems that rust to death may rarely leave behind a statue (ideally made of iron material) which is implied to be its rusted husk.

Polymorphing while wearing crystal plate mail, leather armor, or iron mail can cause you to merge with the armor and turn into that respective material of golem (glass, leather, or iron), with the armor returning unbroken when you revert back to your normal form.

Rust monsters have a one-way grudge against iron golems.

Eating a rust monster while polymorphed into an iron golem is instantly fatal to your polyform.

Rock piercers instakill stone golems, glass piercers instakill glass golems and iron piercers instakill iron golems.

Potions of oil heal iron golems when quaffed.