I'm surprised everyone is talking about galvanize and not what makes Magnizone so good. Magnet pull trapping steels other than skarmory and just killing them with eq.
The problem is that most Steel types have so high defenses that Golem struggles to take them down.
252+ Atk Golem Wild Charge vs. 252 HP / 252+ Def Skarmory: 174-206 (52 - 61.6%) -- 98.4% chance to 2HKO after Leftovers recovery
252+ Atk Golem Thunder Punch vs. 252 HP / 252+ Def Skarmory: 146-174 (43.7 - 52%) -- guaranteed 3HKO after Leftovers recovery
Skarmory can just Roost (removing the Electric weakness) till Golem kills itself with Wild Charge recoil or Whirlwind Golem away if it runs Thunder Punch. If Skarmory carries a Rocky Helmet, then it is even worse for Golem.
Same for bulky Mega Scizor (this isn´t even taking into account the possibility of escaping with U-Turn or Superpower).
252+ Atk Golem Stone Edge vs. 248 HP / 16+ Def Mega Scizor: 114-135 (33.2 - 39.3%) -- 100% chance to 3HKO
252+ Atk Golem Wild Charge vs. 248 HP / 16+ Def Mega Scizor: 102-121 (29.7 - 35.2%) -- 21.8% chance to 3HKO
And Ferrothorn easily lives an Earthquake. If you want to kill Ferro and Scizor with Fire Blast, even max special attack investment only is a 2HKO, not sure if that is really worth it. Ferro 2HKOes you with Power Whip, too.
And any offensive Steel type easily crushes it with Earthquake.
I still really want to try out Magnet Pull Golem. But so far Klefki without Magnet Rise and Choice-locked Magnezone (as long as it is not locked into Flash Cannon) are the only OU Steel types it can eliminate without problems.