The Iron Hands of all the Space Marine Legions maintained perhaps the closest ties with the Mechanicum as was evident with the emphasis they placed on the use of machines and esoteric weaponry within their arsenals. This bond is exemplified non more so than with the Iron Fathers.
The honorific of Iron Father exists outside of the established Legion hierarchy and is bestowed upon those individuals, most notably from within the Legion Forge Lords and Techmarine ranks, that display the greatest affinity with machines and how best to utilise them to further the Legions ends. Their position grants them access to equipment normally reserved for the highest Legion masters and on the battlefield they can be seen in the thickest of action dealing death with weapons born of arcane technology. Their prodigious knowledge of all things mechanical means that they are as adept at making battlefield repairs as they are at smashing aside the enemies of the Iron Hands in combat.