Here are five key things investors need to know to start the trading day:

Tariffs aren't stopping Walmart. The U.S.' largest grocer and private employer hiked its full-year outlook for earnings and sales on Thursday, even as levies push up costs. The Arkansas-based retailer beat Wall Street's expectations for second-quarter revenue, but shares of the company still dropped more than 3% before the bell. Walmart's results mark the end of a string of earnings reports from major retailers this week -- a closely watched indicator for clues into the health of American consumers. Follow live markets updates here.