I appreciate your upfront honesty. Have seen your posts, you definitely have good knowledge in astrology. No doubts.
Actually Iron and Steel are metals of Saturn so they gel well with Blue Sapphire, other metals will not. Also, no jeweller will make an iron ring or steel ring because it will not pay them well or may be its not possible to get it done for reasons known to them; that is why 99% people wear in gold or silver. Never follow the rule i.e. majority is best; because we never know the reason why the majority does it, by choice or compulsion.
Wishing you good luck, may God bless you and over all!