Check out the companies making headlines before the bell: Opendoor Technologies — The online real estate startup popped more than 13%, extending a rally powered by retail traders chasing meme stocks. Opendoor, which has often been cited on Reddit's WallStreetBets forum, is ahead more than 500% this month. Trading volume exploded to 1.9 billion shares Monday, more than 1,700% of the three-month average, according to FactSet. General Motors — Shares tumbled nearly 4% despite the automaker beating sales and profit expectations in the second quarter. Adjusted earnings before interest and taxes of $3.04 billion were higher than analysts estimated, but down more than 31% from a year ago. Lockheed Martin — The maker of the Air Force's F-35 fighter bomber dropped 8% after quarterly revenue of $18.16 billion trailed analysts' consensus estimate of $18.57 billion, according to LSEG. Earnings per share of $1.46 weren't comparable to estimates. Lockheed also reported a $1.6 billion loss attributed to some defense programs, and management said the "ongoing program review process identified new developments that caused us to re-evaluate the financial position on a set of major legacy programs." Coca-Cola — The soft drink maker dipped premarket after Coke topped Wall Street estimates for quarterly revenue and earnings. Coke also reiterated its full-year forecast for organic revenue growth and narrowed its outlook to the top end of its prior range for comparable earnings per share. NXP Semiconductors — The Dutch semiconductor maker dropped 6% after second-quarter sales declined due to slow demand in the automotive market. Otherwise, NXP beat on the top and bottom lines, with adjusted earnings of $2.72 per share on revenue of $2.93 billion exceeding $2.67 in earnings per share on $2.90 billion in revenue expected by analysts polled by LSEG. Steel Dynamics — Shares retreated nearly 2% after the steelmaker's second-quarter results trailed expectations, with $2.01 in earnings per share missing the Street's $2.10 and revenue of $4.57 billion trailing the consensus for $4.76 billion. Medpace — The outsourced clinical development services provider soared more than 45% after second-quarter net income and revenue topped analysts' estimates and it raised full-year guidance. GAAP earnings of $3.10 per share exceeded the FactSet consensus estimate of $2.98, while revenue of $603.3 million beat an expected $538.8 million. CSX , Norfolk Southern — Shares of Jacksonville, Florida-based freight railway CSX rose about 4% on a Reuters report that it is in talks to bring on financial advisors amid speculation about further consolidation in the industry. Norfolk Southern shares were marginally higher after The Wall Street Journal said Union Pacific is reportedly exploring a bid for the rail line . D.R. Horton — The homebuilder surged 7% after fiscal third-quarter results came in above expectations, with earnings of $3.36 per share exceeding the $2.89 anticipated by analysts surveyed by FactSet. Revenue of $9.23 billion topped the estimated $8.75 billion. PulteGroup — Shares popped 1% after the home construction company posted second-quarter earnings of $3.03 per share, topping analysts' estimates of $2.96, per LSEG. PulteGroup's $4.40 billion in revenue also came in ahead of the expected $4.39 billion. Northrop Grumman — Shares jumped 3% after Northrop Grumman posted second-quarter revenue of $10.35 billion, topping the LSEG consensus estimate of $10.07 billion. Zions Bancorporation — Shares rose almost 3% after Zions posted second-quarter earnings of $1.63 per share, beating an LSEG consensus estimate of $1.31 per share. Zions' CEO Harris Simmons said, "We're incrementally more optimistic about growth in the back half of the year than we'd previously been." Albertsons Companies — The grocery chain rose 2.2% after UBS upgraded Albertsons to a buy from neutral, and raised its 12-month price target to $27 per share, implying upside of 35%. Agilysys — Shares sank 11% after the hospitality software company's first-quarter earnings before interest, taxes, depreciation and amortization, or EBITDA, of $12.5 million lagged the FactSet consensus estimate of $14.0 million. Calix — The telecommunications firm rose 3% after quarterly earnings of 33 cents per share topped analysts' estimates of 21 cents, according to FactSet. Revenue of $241.9 million was more than the $223.9 million expected by analysts. — CNBC's Lisa Han, Alex Harring, Spencer Kimball, Yun Li and Tanaya Macheel contributed reporting.
