Some stocks were moving on company-specific news.
CSRA soared 31 percent Monday after news General Dynamics would acquire the government IT contractor for $6.8 billion.
Cboe Global Markets gained 3.3 percent Monday, steadying after a drop of 20 percent last week. The exchange reported quarterly results that narrowly missed expectations, after reporting higher expenses.
Some of the exchange's better known products are focused on market volatility. Many hedge funds and individual investors bet heavily on calm markets, and found themselves on the wrong side of the trade when the Cboe Volatility Index (.VIX) spiked to its highest in more than two years Tuesday.
Major U.S. stock indexes climbed nearly 5 percent or more Monday from their lows hit Friday, when stocks posted their worst week in two years.