Forget stocks, forget gold, forget oil, because for Dennis Gartman, there is one commodity every investor needs to own: aluminum.

"Buy aluminum first," Gartman said. "That's the best commodity trade out there."

In an interview with "Futures Now" on Tuesday, the Commodities King said aluminum is not only the best way to play the record run in stocks, but could also be the best proxy for investing in the global recovery.

"Everyone laughed at me when I started buying aluminum nine months ago," joked Gartman. "You are going to see a larger off take of aluminum going into automobile production. It's the easiest way to meet EPA requirements for mileage is to make the automobiles and trucks lighter, and aluminum does that relative to steel and you're going to be selling, we're going to be selling, everybody's going to be selling a lot of automobiles for the Chinese."

Aluminum futures are on a tear this year, up nearly 11 percent, outpacing gold, silver, copper and stocks.

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And according to Gartman, aluminum may have even replaced copper as the best commodity to measure economic growth.

"You know, you always hear people say that copper is the commodity with a Ph.D. in economics, I've always said, really, it's got a master's degree. When you look at aluminum, zinc, tin and copper combined then it gives you an idea of what's going on in the global economy and aluminum, zinc and tin are very strong."

In terms of the broader stock market, Gartman's plans for making money remain very simple: just buy stocks.

"It will continue until it stops. And honestly, that's 45 years of experience."

—By CNBC's Amanda Diaz.

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