When Janet Yellen speaks, investors tend to listen. Markets emphatically approved of what the Federal Reserve chairwoman had to say on Monday, as seven in 10 stocks advanced and all 10 sectors finished with gains. Yellen all but assured the financial world that low interest rates were here to stay, which should help facilitate economic growth. But even in this state of euphoria, Newmont Mining (NEM -0.52%), Netflix (NFLX -2.52%), and Denbury Resources (DNR) still managed to lose ground on Monday. The S&P 500 Index (^GSPC -1.20%) did not lose ground, gaining 14 points, or 0.8%, to end at 1,872 today.

Newmont's Boddington gold mine.

Shares of Newmont Mining, a gold and copper miner, lost 2% today. Like any other mining company, Newmont's gains and losses are largely simple functions of the prices of the commodities it mines for. Despite the upbeat stock market, investors found it hard to get bullish on Newmont on a day when both gold and copper prices retreated. On top of this, conflicting accounts about whether or not Newmont's copper production in Indonesia has been hit by new tax laws is confusing investors. Newmont denies the claims, made by an Indonesian government official last week. 

Netflix shares shed 1.9% today; the stock has tumbled more than 7% in the last week as concern mounts that big-time competition is on its way. Recent reports from the Wall Street Journal cite both Apple  and Amazon.com as working to improve or develop streaming services to compete with Netflix's offerings. While Amazon denied reports that it was working on a free streaming service, Apple does appear to be negotiating with Comcast (NASDAQ: CMCSA) on a deal for high-quality streaming TV on its set-top boxes.

Lastly, shares of Denbury Resources dropped 1.6%, a dip large enough to make it one of the S&P's weakest performers. Like Newmont, Denbury's performance as a stock is subject to the daily fluctuations of the materials it extracts. A U.S.-based oil and natural gas producer, shares didn't respond well to natural gas's 2.5% decline today. From a long-term perspective, Denbury remains well-positioned for the future, as a new era of American energy independence bodes well for domestic energy producers. Not only does their location give them transportation cost advantages over foreign competitors, but sheer production volume also should allow for more export opportunities to arise.