Image: National Oilwell Varco.

The stock market has recovered a huge portion of its losses from earlier in the year, and Monday brought continued enthusiasm to investors looking for gains. The rise for major market benchmarks like the S&P 500 was modest, but gains pushed the index above the 2,000 mark for the first time in two months. Continued gains in the commodity sector of the market showed the reversal of sentiment that we've seen in recent weeks, and now, many bullish investors have pushed past concerns about a major correction to the sidelines. In particular, shares of National Oilwell Varco (NYSE:NOV), PRA Group (NASDAQ:PRAA), and Cliffs Natural Resources (NYSE:CLF) were among the best performing stocks on Monday.

National Oilwell Varco climbed more than 7% on Monday, responding to the recovery in the energy markets. Crude oil prices moved above the $40 per barrel mark on the international markets for Brent crude, and gains in the U.S. market also pointed to the potential for a substantial rebound from 2015's huge plunge in the energy markets. As a key supplier to oil and gas exploration and production companies, National Oilwell Varco has seen demand for its goods and services fall along with crude as its customers have pulled back on capital expenditures. If oil can continue to recover, however, then those companies will likely put their production back on line, and that in turn will lead to Varco getting more business from its client base going forward.

PRA Group jumped more than 11%. The debt-collection specialist has regained all of the ground it lost following its fourth-quarter earnings report and then some, and investors have seemingly moved past the concerns they had about PRA's ability to keep generating growth in a tough market environment. The balancing act that PRA Group has to walk is that it needs economic conditions to be uncertain enough to prompt potential customers to sell collectible assets to the company that it can then use to generate profits, but those conditions can't be so bad that they make PRA Group's collection efforts doomed to failure. Now that the financial markets have started to stabilize, investors seem more comfortable that PRA Group will be able to weather current conditions and find growth opportunities in the near future.

Finally, Cliffs Natural Resources jumped 19%. The producer of iron ore saw its shares respond favorably to reports that the Chinese government will attempt once again to stimulate growth in the world's second-largest economy. Given the importance of China to the global commodities markets, it's reasonable for investors to believe that stimulus efforts could center on stoking demand for construction and infrastructure projects that require substantial amounts of steel. However, the much larger question for Cliffs is whether the U.S. market will rebound along with China, because Cliffs has increasingly focused on the domestic market and its more stable pricing. Favorable global trends could help Cliffs' domestic results as well, but there's still a lot of long-term uncertainty about whether current efforts will prove successful in the long run.

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