The stock market has been struggling all year, and investors have done their best to remain patient while waiting for a rebound. Despite having faced numerous head-fakes recently, markets made another attempt to start the week on a positive note. In the premarket session before regular trading began, futures contracts on the Dow Jones Industrial Average (^DJI 0.34%), S&P 500 (^GSPC 0.12%), and Nasdaq Composite (^IXIC -0.07%) were up roughly 1%.

Mondays often bring big moves for individual stocks, as news from the weekend makes investors more or less excited about the prospects for fundamental businesses. A couple of companies were in the spotlight this Monday, leading to big gains in share prices for Splunk (SPLK) and Archaea Energy (LFG). Below, you'll learn everything you need to know about what's prompting these gains and whether there could be more ahead.

Splunk gets some activist interest

Shares of Splunk were up nearly 10% in premarket trading early Monday morning. Like many companies in the technology space, the data management specialist has seen its stock struggle over the past year. However, it appears that a well-known institutional investor wants to do something to turn Splunk around -- and that investor is putting its money where its mouth is.

Splunk's move higher came amid reports that investors at Starboard  Value have bought almost 5% of the software-as-a-service  provider's stock. Those watching the company are speculating that Starboard is going to seek action from Splunk's board of directors and executive management that will help the share price pull out of its recent dive, having lost more than a quarter of its value in just the past month and fallen by more than half since late March. Starboard wouldn't be the only institution with a big interest in Splunk, as private equity specialist Hellman & Friedman has had a nearly 8% position in the software company for a while now.

Shareholders have had to endure challenges in Splunk's leadership ranks, including last month's resignation of CFO Jason Child. However, Splunk has considerable business strength, with a fast-growing addressable market and considerable loyalty among current customers in renewing their subscriptions and expanding their use of its software platform. Clients will still need the insights that Splunk's software offers even in an economic slowdown, and that suggests there could be more room for the stock to climb if Starboard's suggestions have merit.

Archaea gets a buyer

Archaea Energy was the big winner on Wall Street Monday morning. The renewable natural gas specialist's shares jumped more than 50% on news that it had received a buyout bid from a major company in the oil and gas space.

Archaea announced that it had entered into an agreement with U.K. energy giant BP (BP 1.02%) under which BP will acquire Archaea for roughly $4.1 billion. The deal, which will include BP's assumption of about $800 million in debt, will pay Archaea shareholders $26 per share in cash.

From Archaea's perspective, the acquisition will open up huge resources for it to expand its renewable natural gas capabilities. With more capital, Archaea expects to accelerate its growth plans and take advantage of BP's vast customer base. Meanwhile, BP has been working to expand its bioenergy business, and the Archaea acquisition will be a big jump forward for the U.K. company as it aims to differentiate itself from other major oil companies.

The acquisition bid comes just over a year after Archaea went public through a special purpose acquisition company. The acquisition will be a nice payday for shareholders, but unless a competing offer starts a bidding war, Archaea investors shouldn't expect any more upside.