Energy firms such as Chevron CVX.N and Exxon Mobil XOM.N have blown past profit estimates this quarter, benefiting from surging energy prices, as opposed to Big Tech firms that have largely disappointed investors. By Amruta Khandekar Oct 31 (Reuters) - U.S. stocks fell on Monday, potentially stalling a two-week rally in the S&P 500 and the Nasdaq indexes, as investors turned cautious ahead of the Federal Reserve's rate-setting meeting this week. A policy decision from the Fed is due on Wednesday, with investors expecting a fourth straight 75-basis point interest rate hike to curb decades-high inflation.