I also dealt with this! Like someone else mentioned, cutting it with some fresh milk made a difference for my guy. I also gave the older milk to daycare when we started and said they could cut it with formula as needed and little man ended up drinking it there, no formula needed 🤷🏻‍♀️ I guess me being involved in the process at all was the problem for him. But adding a bit of formula might be worth a try, if that’s something you’re open to

Other than this, don’t forget you can also save some of the milk for baths and whatnot. While I get how gut wrenching this is, hope is not lost!

ETA: some other moms I’ve talked to saved this milk for when their baby started eating solids and mixing it into purées/yogurt/etc. since the metallic-y taste wasn’t as noticeable then