I have used 6 in 1's ever since someone pointed me out to them on this board and have yet to experience a bad can or batch. I usually buy them at the local supermarket but always found them to be fresh and somewhat sweet in taste and smell.
I've tried other brands, well...almost any brand I could get my hands on here in SF actually, but the 6 in 1's is so far my preferred brand. Never had any metallic taste or even fishy smell come out of a can.
Send them an e-mail and make them aware of your problem. I'm sure they would want to remedy that problem.
There's a risk of using the contents of a dented can. If I see anything dented on a supermarket shelf, whether it's canned tomatoes, canned pet food or canned anything, I won't buy it.