Eli -
"why zinc" ? Honestly, I don't know.
Someone recommended it to me when I had metallic mouth and I took it.
The issue finally went away. However, I really don't know if it was just time for it to leave or if the zinc actually worked.
Since the zinc won't harm you, and it might just help you, I say give it a try. You've got nothing to lose - but the metallic taste in your mouth.
Good luck,
Jan