Oil Prices Drop Below $53 Per Barrel

U.S. markets closed in the red Monday, but in a far less shade of crimson than when they first opened. Following a long holiday weekend and a "no" vote in the Greek referendum, the Dow tanked and, at its worst point, fell more than 165 points. However, all the major indices managed to erase the worst losses. The Dow still remains in the red for the year.

Oil saw its biggest drop in five months in reaction to a couple of things: Greece's referendum vote, a strong U.S. dollar and too much supply. Crude fell 7.73%, or $4.40, Monday to settle at $52.53 per barrel. It was oil's lowest settle since April 13.

Energy was the biggest losing sector Monday. Oil and gas drillers as well as exploration and production stocks were among the biggest losers in the energy sector Monday, including Transocean, Pioneer Natural Resources, Helmerich & Payne, Diamond Offshore Drilling and Marathon Oil.