The Iron Monger is a suit of armor based on Iron Man's one. It has been donned by several people, two of which have been involved in Captain America's adventures.
This part of the article contains info not directly related to Captain America, his allies or his enemies. However, this info is necessary to provide context to the rest of the article.
The first and best-known Iron Monger was Obadiah Stane, a businessman who took over Stark Enterprises. After Iron Man defeated Iron Monger and got evidence of his corrupt activities, Stane killed himself instead of facing justice.
When John Walker returned the Captain America The Avengers identity to Steve Rogers, General Hayworth bought an Iron Monger armor to Stane International, gave it to a Guardsman named Gregory Smoot and had Smoot fight Walker, now under the identity U.S. Agent as a show of Walker's abilities to the other members of the Commission on Superhero Activities.
Cristoph Pfeifer was an agent of the Red Skull who donned the Iron Monger armor.