Image: Alcoa.

The stock market began the week with solid gains on Monday, and the positive mood of investors was squarely focused on rebounds in key sectors that had seen the biggest downturns during the past several months. In particular, crude oil prices jumped more than 5%, continuing to carry prices into the $30s, and trying to convince investors that a bottom for energy prices has either already been reached, or is imminent. Among some of the stocks that posted the biggest gains on Monday were Alcoa (AA), Marathon Oil (MRO -2.36%), and Teck Resources (TECK 0.15%).

Alcoa jumped 13% as investors looked to the hard-hit aluminum market as being one with the largest potential for a bounce. Alcoa, in particular, could enjoy outpaced gains in the future, especially as it plans to go forward with its split into two separate companies. With one company set to focus on raw materials like alumina, a gain in commodities could come at exactly the right time, driving interest for a pure-play on better conditions in the aluminum and other commodities markets.

At the same time, the second company will concentrate on Alcoa's current value-add market, which has ample opportunity to tap into the growth in aerospace and automotive demand, regardless of what happens with aluminum prices. Given how long Alcoa has slumped due to low aluminum prices, even a glimmer of hope is enough to make investors excited about its opportunities to rebound.

Marathon Oil rose 11%, regaining all the ground it lost late last week after it released its fourth-quarter financials. Marathon lost $869 million in the fourth quarter even after adjusting for extraordinary items, and it announced at the same time that it would reduce its capital expenditure program by more than half, to just $1.4 billion for 2016.

Like many oil companies, Marathon is focusing on protecting its balance sheet from credit-related challenges, and giving itself as much flexibility as possible to take advantage of any strategic opportunities that might arise. Key areas like the Eagle Ford will be the primary target of Marathon's spending; but because of the general pullback, the company expects total production to fall 6% to 8%, even after adjusting for assets it divests during the year. Today's oil-price gains raise the possibility that Marathon will be able to avoid more extreme measures, but it's too early to tell whether an upward move for crude will be sufficient.

Finally, Teck Resources climbed 15%. The Canadian mining company has exposure to copper, as well as other base metals like molybdenum and zinc, and most of those markets are performing well today. One reason why Teck Resources investors are confident about its ability to benefit from price gains in the commodities markets is that company management has been adamant about saying that it expects not to have to issue new equity at bargain-basement prices in order to raise capital.

Many miners haven't been as lucky, needing to do secondary offerings, even though they've diluted existing shareholders. If Teck can manage to make it through the entire downward part of the cycle without issuing new equity, it will make the eventual profits more lucrative when markets start to turn.