No, they do NOT. tell one metal (aluminum ) apart from another (gold). All that any metal detector can do is tell conductivity . And unfortunately , various metals shares conductivities . Sheesk, if some folks are going to swoon and wax romantic with advertising. claims , why not just go get one of those Whites , that. "tells you what's in the ground before you dig it " ? haha
And as far as showing 3d shape: The problem is pixel size . The utmost smallest pixel is about 1" across . Hence all coin-sized objects (nails , rings , tabs , foil wads , etc....) will all be .... doh ... 1 pixel !
Even things you might THINK. would have a revealing shape (like a horse shoe ), is nothing more than a messy blotch of pixels .