I love that we're all "What did you cook it in?" as a first guess. SS won't impart that flavor, and the OXO food mill is also stainless.
Last year I had a batch with a similar metallic taste at the end, made w similar ingredients; fermented yellow supers, onion, garlic, pineapple, rice wine vinegar, clover honey. Tasted great up front, tasted like sucking on pennies at the finish.
Tried to add more vinegar/honey to help soften that finish but wasn't ever completely satisfied with the sauce and ended up throwing the whole batch out before bottling.
- The Hot Pepper likes this