Only thing behind my metal I put on is studs and insulation than plastic, seems like a lot of work if don't have OSB, plywood or sheetrock. Framing out wood on studs to get box where needed is way to much not fun kinda wondered have helped many friendsHave to take the existing box off, remove wires from outlet, pull old box out out and then install new box and reinstall outlet. Snap in box has screws top and bottom that have a flange and will clamp itself to sheetrock or OSB. Whatever is behind the metal.