Iron Golems are the strongest golems after adamantite golems . They require +3 or greater weapons to hit them; for example: Flail of Ages, Carsomyr, Runehammer, Crom Faeyr, etc. Some locations of iron golems are: the de'Arnise Keep, possibly in the Windspear Hills dungeon, etc. Iron golems are the same size as adamantite golems. They have some physical damage resistance, but not even close to the resistance of adamantite golems. They have a high magic resistance but are vulnerable to Melf's Minute Meteors.
Due to their huge size, Iron Golems are prone to get stuck at doorways. One should use this to their advantage - use one hasted party member to lure the golem to the nearest doorway, wait for it to get stuck and pummel it from distance. Bullets +3 and Quarterstaff +3 or better, due to their length, as well as the Dwarven Thrower are the best weapons to use, since the characters will be out of range to the golem.