Just want to caution you as I don't know how handy you are, but you should know the basics about electrical wiring as that aspect is exactly the same as creating an outlet box anywhere if you do this from scratch.
In terms of creating the opening for the box, with metal it would depend on the thickness, and may be tricky getting a clean cut, but a drill and tin snips may be the first thing to consider... or a dremel... metal gets hot, very hot, when you try to drill or dremel, though. Plastic may be easier to create the opening with.
Please make sure you are using GFI outlets or are on a circuit that has one as it is in the bathroom, as code would require (and you want that anyway).
Our outlet is simply a regular outlet box for construction/siring purposes, just happens to be inside the cabinet.
Q
