Early morning earnings reports from major financial companies and a few economic reports, including industrial production, could set the tone for Wednesday's markets.
But ahead of that, traders will be watching an overnight report on China's first-quarter GDP and the outcome of the European Central Bank's meeting and 8:30 a.m. ET press briefing, just ahead of the New York opening bell. The ECB is not expected to take action, but it could discuss quantitative easing, and that could affect the currency market.
The oil market and the dollar could also be factors for markets, after a flare-up in crude futures prices Tuesday helped give energy stocks and the broader stock market a lift. The dollar slipped after moving higher against the euro early in the day.