Metal studs are used in commercial work because of their fire resistance and because they only hold up drywall. Shelving is typically modular, and the only things hanging from the walls are pictures. The thin walls of average metal studs will not support too much weight, in my opinion, however, heavier guage studs are available, but at a price. Also, wood is a better insualtor, and will not radiate cold like the metal studs. Additionally, attaching insulation will prove much easier with wood. Good Luck.