Stocks end down after biggest month in 2 years

STORY: Wall Street ended slightly lower after a volatile session Monday, as investors digested the U.S. stock market's biggest monthly gains in two years.

The Dow and Nasdaq ended down fractionally, while the S&P 500 ended a little more than a quarter of a percent lower, as some investors became more cautious in the wake of last week's rally.

Peter Andersen is founder of Andersen Capital Management.

“Well, the question about why the volatility today compared to last week, this is a very, very unusual period. I think we have to throw out the so-called playbooks of our past experience, simply because we are emerging from a worldwide pandemic. And although I would like to desperately find patterns and what we are experiencing, it's anybody's guess the day-to-day volatility, I think some days we will find periods of very smooth, gradually rising stocks. Other days the opposite. And then, of course, we'll find days where it's all over the map, so to speak, with very, very large volatility, depending upon any tiny or large news item of the day. It's a very, very sensitive market right now we're experiencing.”

Oil prices fell Monday on demand concerns, which in turn weighed on energy stocks - making the sector the deepest decliner on Monday.

Shares of Boeing gained after Reuters reported the FAA approved the planemaker's inspection and modification plan to resume deliveries of 787 Dreamliners.

Shares of Roku, which plummeted more than 20% on Friday after posting dismal earnings, gained big Monday after Cathie Wood’s ARK Innovation fund said it was adding to its position following the steep selloff.

And shares of Pinterest rose Monday but soared 20% higher in extended trading after the pin-board platform posted better-than-expected user numbers even as earnings and revenue came in lower than estimates.