Commodity markets were a large driver behind the move, as front-month crude oil fell more than 3.5 percent to lows of 81.17 from morning highs over 86.50.
The S&P 500 dropped 16.73 points, or 1.26 percent, to close at its session low of 1308.93. The SPX had traded as high as 1335.52 early in the day.
The Nasdaq 100 also ended at its session low of 2517.18 after plunging 42.03 points, or 1.64 percent. Shares of market leader Apple fell sharply into the close, finishing the day down nearly $10 from Friday's close to $571.17 after opening above $588.
The Russell 2000 lost the most ground on a percentage basis, tumbling 2.36 percent, or 18.18 points, to settle at 751.01.
S&P 500
Resistance is now 1313.43, followed by 1315.12, 1318.25, 1320.22, and 1325-1330.Nasdaq 100
Support is now 1308, followed by 1305.15, 1301.75, 1300, and 1298-1290.
Resistance is now 2518.32, followed by 2528.30, 2535, 2547.05, and 2550-2579.23 (yesterday's high).Russell 2000
Support is now 2515, followed by 2508.15, 2500, 2498.12, and 2490.
Resistance is now 751.98, followed by 755, 757.10, 760.01, and 765.15.
Support is now 750, followed by 748, 746.50, 743, and 740.
