Walmart, the world's biggest retailer WMT.N, gained 3.5% in premarket trading after raising its full-year earnings forecast as additional stimulus checks increased spending for apparel and electronics. By Medha Singh May 18 (Reuters) - Wall Street's main indexes were set to open higher on Tuesday after better-than-expected results from Walmart and Home Depot signaled strength in consumer demand against the backdrop of rising prices. "The market still remains fearful of runaway inflation and the narrative is driven by the game of catch-up from the supply chain side while fundamental earnings and GDP performance are not back at pre-pandemic levels."