Robinhood (HOOD) stock gained more than 15% on Monday, closing at a fresh record high on the news that the company will soon be included in the S&P 500 (^GSPC). Robinhood, AppLovin (APP), and Emcor (EME) are set to join the S&P 500 during the index's next rebalancing on Sept. 22, S&P Dow Jones Indices said in a statement Friday. The three companies will replace MarketAxess Holdings (MKTX), Caesars Entertainment (CZR), and Enphase Energy (ENPH). AppLovin closed the day up more than 11%, while Emcor stock ...