Silver war-hammers are the best thing you can use against armored opponents, easily crushing a helmet into someone's skull. Some rough testing on the wiki seems to indicate that silver warhammers are un-par with ADAMANTINE axes, at least against unarmored opponents. Ofc... with the right grooming and micromanagement of stocks, you can get platinum warhammers... which would be even deadlier due to DF's simplistic physics. In fact, if I start in a !FUN! embark I'll often take either tetra or galena with me. I'll melt them down for the silver, and make a squad of silver hammer-dorfs with it. Iron is 24 points of 4 bars and steel includes taking flux and far more fuel per bar... and is STILL weaker than those silver hammers.
That being said, armor user and shield are the two most important ones to take- far more than taking ranks in weapon skills. First, without armor user you can't give your dorfs a full suit of metal armor without forcing them to crawl across the battlefield before passing out from exertion. Also, shields are overpowered and the single best thing you can give a dorf to keep him alive. Masterwork weapons bring with them a x2 multiplier to attack as well to help compensate for lower attack skills at first. Bring your proficient weaponsmith that loves bronze/silver/iron/steel (or w/e specific weapon you want to make) and have him churn out/recycle metal until you get those masterworks. Keep in mind, a dorf that loses an arm or eye will never recover outside of lycantrhopy. A legendary axelord with only one arm and impaired grasp in the other trying to gauge depth-perception with a single eye is a pathetic thing. Dorfs with low armor skill can still safely equip helmet/boots/gloves out of metal with bone/leather for the rest. Shields should never be made of anything but wood (featherwood and willow preferred). Yes, copper shields bash for more damage. However, your dorf shouldn't be bashing with his shield. He should be bashing with his hammer. In the meantime, those heavy copper shields can and will slow him down/wear him out quicker.
I usually do a 2/5/3 split with weaponskill/armor/shield if I expect early trouble. This ensures they pick up the right weapon and have enough armor-user to comfortable put on a metal breastplate and greaves on top of the other metal equipment. Top off the uniform with at least one cloak for good measure.