Stocks held modest gains as a rally in crude oil propelled the energy sector higher. 

The S&P 500 was up 0.25%, the Dow Jones Industrial Average added 0.2%, and the Nasdaq gained 0.2%.

Stocks had been lower around midday before jumping back into positive territory. Markets have seen jittery trading in recent weeks.

"Stock prices have been stuck in neutral for the last six weeks, as investors await signs that economic and earnings growth can catch up to recent price gains," said Robert Doll, chief equity strategist at Nuveen Asset Management. "Markets seem to be taking a pause to see if the economy and profits can catch up to the latest valuation expansion." 

Energy shares were the best performers on Monday. Crude added to last week's 3% gain, trading at its best levels in roughly a month. West Texas Intermediate crude was up 1.6% to $53.08 a barrel, while major oil companies including Exxon Mobil (XOM) - Get Report , Chevron (CVX) - Get Report , Hess (HES) - Get Report  and ConocoPhillips (COP) - Get Report rose. The Energy Select Sector SPDR ETF (XLE) - Get Report added 1.1%.

Gains in Tesla (TSLA) - Get Report shares buoyed consumer stocks. Tesla added more than 3% on Monday after Piper Jaffray upgraded the shares to buy from neutral and increased its price target to $368 from $223. Analyst Alexander Potter said the electric automaker may begin deliveries of the Model 3 this year rather than mid-2018. Tesla shares added 3%. 

The rest of the cyclical consumer goods space was also on the rise on Monday. Fellow automakers Toyota (TM) - Get Report , General Motors (GM) - Get Report , and Ford (F) - Get Report were also higher, while the Consumer Discretionary SPDR ETF (XLY) - Get Report added 0.5%. 

Citigroup (C) - Get Report , JPMorgan (JPM) - Get Report and Wells Fargo (WFC) - Get Report will report their performance over the three months through March on Thursday, the final day before Wall Street takes a three-day Easter weekend. The banks are the first to report earnings this season.

Citigroup and Wells Fargo are holdings in Jim Cramer's Action Alerts PLUS Charitable Trust Portfolio. Want to be alerted before Cramer buys or sells C or WFC? Learn more now.

Hopes are high for another period of growth for companies in the S&P 500. Operating income is expected to increase more than 9% during the first quarter, according to FactSet, the fastest pace in just over five years. Another period of growth would mark the third straight quarter of earnings gains.

Wells Fargo moved slightly lower after holding back $75 million in pay from former CEO John Stumpf and former retail bank executive Carrie Tolstedt, the two executives most prominently tied to the bogus account scandal at the bank. Stumpf, who had already forfeited $41 million when he resigned in October, had been made aware of the toxic account culture in 2012 and had knowledge of specific fraudulent account cases as early as 2002, according to the investigation.

Straight Path Communications (STRP) rocketed 150% higher on Monday after AT&T (T) - Get Reportagreed to purchase the company in a $1.6 billion deal. Straight Path holders will receive $95.63 in AT&T stock for every share outstanding. The deal is expected to close within a year. AT&T shares dragged on telecoms.

Whole Foods (WFM) jumped 9% on Monday afternoon on reports activist investor Jana Partners had built its stake and was pushing for board changes.  The Wall Street Journal said Jana has urged the supermarket chain to even consider a sale. 

Geopolitical concerns continued to weigh on Wall Street, following U.S. intervention in Syria last week. About 60 cruise missiles were launched at the al-Shayrat airfield on Thursday evening, the air base identified by the U.S. as the location from which a chemical attack that killed dozens was launched.

The attack by American destroyers USS Ross and Porter was the first time the U.S. has involved itself directly in Syria's long-running civil war.

Russian and Iranian forces warned in a statement published on Ilam al Harbi over the weekend that the action had crossed "red lines" and they would respond to further attacks.

Meanwhile, the Trump administration appeared to approach the crisis from different angles. U.S. Secretary of State Rex Tillerson said that the missile attack was a warning to the Assad regime that the U.S. would not tolerate chemical warfare.

However, he said, "there is no change to our military posture." Tillerson also called on Russia to "fulfill its commitment" to a chemical weapons ban enacted in 2013. The Russian government backs the Assad regime. 

U.N. Ambassador Nikki Haley took a harder stance, noting on CNN on Sunday that there was no political solution with "Assad at the head of the regime."

Also over the weekend, bombings of Coptic churches in Egypt killed more than 40 and injured 100, with ISIS claiming responsibility for the attacks. Egyptian President Abdel Fattah el-Sisi has declared three days of nationwide mourning and will call for a three-month state of emergency. 

During the rest of the week, Federal Reserve Chair Janet Yellen headlines a period of relatively little policy talk. Yellen will speak at the University of Michigan's Ford School of Public Policy today and may take audience questions. Investors will be on the lookout for commentary on the pace of rate hikes this year and any hints as to when the central bank will begin to reduce its balance sheet.

Rent-A-Center (RCII) - Get Reportadded 6% on Monday after appointing Mark Speese as its new CEO. Speese was approved unanimously by the company's board. Additionally, the rent-to-own retail chain has announced a new strategic plan designed to drive its growth and improve company profitability.

Barclays (BCS) - Get Report CEO Jes Staley is being probed by the U.K.'s financial watchdogs over an internal investigation into whistleblowing. Shares of the bank were down slightly in trading in London early Monday.

The Financial Conduct Authority and the Prudential Regulation Authority have started investigations into Staley's conduct after an attempt to try to identify a whistleblower.

The Barclays board on Monday said it became aware of the matter in early 2017 when the issue was raised by a concerned employee. 

Lennar (LEN) - Get Reportreduced its first-quarter earnings after taking an unexpected financial hit. The homebuilder, which took a one-time $140 million charge tied to a 2008 court case, will purchase associated property for $114 million. Lennar reduced its first-quarter earnings to $38.1 million, or 16 cents a share, from a previous $130.8 million, or 56 cents a share.  

Swift Transportation (SWFT) surged 23% after agreeing to a stock-swap merger with Knight Transportation (KNX) - Get Report . Both boards unanimously approved the roughly $5 billion deal. Swift stock will convert to 0.72 share of the new company in a reverse split, while Knight will exchange one-for-one. 

Skechers (SKX) - Get Report rose after being upgraded to neutral from negative at Susquehanna Financial. Analysts said the stock is now appropriately valued after falling about 17% over the previous eight trading days.