If you literally buy the metal as @CaptainHarley suggests, then gold and silver are not terrible investments. But this is a cautious investment, as you obviously have to house the metal until you decide to sell it, and you have to find a buyer who will buy actual gold (which can be tougher to do if you expect retail value).
With stocks, take your pick of advice. My money is on solar power, a lot of people like energy companies in general (in particular oil), tech companies, etc, etc.. It’s a matter of who’s advice you listen to.
You could do the roth IRA route, but keep in mind that’s a retirement fund, and you won’t have access to it without penalties, until you retire.
You could also try a savings account or CD. With the CD you can get pretty respectable interest (5% range if you look hard enough), but you can’t get your money til it matures (usually 2 years or so)... The savings account has lower interest but you obviously have access right away.
You could also go the non-investment route, and maybe take a vacation of a lifetime. While it may not show on a bank line, a trip back packing across Europe or Asia (or something of the like) is an extremely valuable experience that most will never have.