What happened Shares of copper and gold miner Freeport-McMoRan (NYSE: FCX) rose just shy of 11% in October, according to data from S&P Global Market Intelligence. Performance, however, didn't go in a straight line across the month. In fact, the stock was up by 17% at one point, just after the company reported earnings. But over the last week of the month the stock headed lower, giving back a portion of its gains. So what It would be easy to suggest that earnings were the problem, but the numbers were actually pretty solid. For example, year-over-year revenues were higher by 22% in the third quarter, with earnings coming in at $0.22 per share up from a loss of $0.15 per share in the same quarter of 2019. That said, the improved performance was largely attributable to increased selling prices for copper and gold, higher by 15% and 28%, respectively. Production of both copper and gold was lower year over year, though the company actually sold more copper in the third quarter of 2020 than it did in the same period of 2019. On the whole, Freeport-McMoRan appears to have had a decent third quarter. So why did the stock start to fall after the company reported results? Image source: Getty Images. The answer is pretty simple and goes right back to the heart of Freeport-McMoRan's business -- it's a miner that sells often volatile commodities. The biggest impact on its business is copper. Copper rose through most of October, but started to head lower over roughly the last week of the month. There's not a lot the miner can do about its relationship with the metals it produces. Investors will always see it as a proxy for copper, and its shares will always trade generally in line with that key industrial metal. In other words, there were no surprises in October for Freeport-McMoRan or its shareholders. The stock did exactly what you'd expect given the price moves in copper. Now what Freeport-McMoRan is one of the world's largest copper miners -- if you are looking to invest in this metal, it needs to be on your short list. However, one month's gain (or loss) isn't really the most important thing you need to consider here, since the stock is likely to track along with the prices of the main commodity it produces. 10 stocks we like better than Freeport-McMoRan IncWhen investing geniuses David and Tom Gardner have a stock tip, it can pay to listen. After all, the newsletter they have run for over a decade, Motley Fool Stock Advisor, has tripled the market.* David and Tom just revealed what they believe are the ten best stocks for investors to buy right now... and Freeport-McMoRan Inc wasn't one of them! That's right -- they think these 10 stocks are even better buys. See the 10 stocks *Stock Advisor returns as of October 20, 2020 Reuben Gregg Brewer has no position in any of the stocks mentioned. The Motley Fool has no position in any of the stocks mentioned. The Motley Fool has a disclosure policy.Source