So, I happened to be reading-up on the Gorgon, which is a monstrous bull-like creature covered in iron plates. From the Monster Manual:
Few creatures that encounter a gorgon live to tell about it. Its body is covered in iron plates, and its nostrils fume with green vapor.
However, the Monster Manual doesn't describe what the Gorgon looks like underneath, or what would happen if the Armor was removed or eaten by Rust Monsters:
The rust monster corrodes a nonmagical ferrous metal object it can see within 5 feet of it. If the object isn't being worn or carried, the touch destroys a 1-foot cube of it. If the object is being worn or carried by a creature, the creature can make a DC 11 Dexterity saving throw to avoid the rust monster's touch. If the object touched is either metal armor or a metal shield being worn or carried, its takes a permanent and cumulative -1 penalty to the AC it offers. Armor reduced to an AC of 10 or a shield that drops to a +0 bonus is destroyed. If the object touched is a held metal weapon, it rusts as described in the Rust Metal trait.
I looked around to see if this question had been asked before, and was suprised to find that it hadn't, so I am going to go ahead and ask it now:
What would happen if a Small Group of Rust Monsters attacked a Gorgon to feed?