Investing in Gold & silver advice needed?

Hello, Im 16, and was thinking instead of having cash laying around, that I should invest in some precious metals rather than leave it there waiting to be spent. However is this a wise investment in 2010, I know the market goes up and down, but Im asking for an estimate from you, Do you think their value will be much more by the time im 21 years old (2014) If not, How long before I could see a return. (I know they dont allways go up)