There are various ways to make thin metals more dimensional while still in a sheet. The ways used would depend on the softness of the metal, the sharpness of the outlines desired, how much continuous space would be made dimensional, etc.
The most common "embossing" for crafts is done with something like a ball stylus embossing tool:
http://www.china-finearts.com/UploadFile/pro/201111/www_1320976567749.jpg
a metal or cardstock stencil, and fairly soft/malleable metals often thin enough to be sold as "foils."
The embossing/impressing of the metal will be done on top of a somewhat soft surface (sheet of fun foam, magazine, etc, depending on effect).
Even regular kitchen aluminum foil can be used (or the heavier duty aluminum foil, or two layers of foil), but more often other foils are purchased at craft and art supply stores.
https://www.google.com/search?q=embossing+foil
https://www.google.com/images?q=metal+embossing
https://www.google.com/search?q=metal+embossing
https://www.google.com/images?q=how+to+do+metal+embossing
https://www.google.com/search?q=how+to+do+metal+embossing
Heavier , softer metals can also be stamped/embossed with metal stamps, and some may be shaped with hammers on anvils, and other tools.
Those techniques create "bas relief" effects though, rather than fully 3D.
http://en.wikipedia.org/wiki/Bas_relief
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