Gold may steal the spotlight when it comes to investing in metals, but there is also silver. And let's not forget "Dr. Copper" -- so named because of its uncanny ability to predict the broad economy. And then -- there are gold stocks, platinum, palladium and aluminum (or aluminum, if you live across the pond). All of these are biggies, and here are some free resources to help you navigate them.
Strong liquidity and a mass following means metals markets often reflect Elliott wave patterns very clearly. Learn how to exploit a trend for as long as it's in progress.