I like to add more info to the "Answers" Page about the Rare metal Shards. For the hell of it, I equipped all my characters with "Lucky charms (Item drop rate buff)" And I found a Golden Mimc at random. Just like to throw that out there. since i am still looking for them damn metal shards --- "Fear is a Mind Killer"
They are located in all Closed Roads. They'll show up very rarely. You get the Rare Metal Shard from shooting off the gold box around him and not from actually killing him. --- "Sometimes you have to take 1 step backwards to make 2 steps forwards."