These are the stocks posting the largest moves in midday trading. : General Motors — Shares of the automaker surged 9% after the announcement that Microsoft was investing in Cruise, GM's autonomous vehicle project. As part of the deal, Microsoft will be the preferred cloud provider for Cruise and GM. American Express — Shares of American Express jumped 3.5% in midday trading after JPMorgan issued an upbeat note on the payments company and advised investors to buy the stock.