The U.S. stock market closed a volatile day of trading on a mixed note. The S&P 500 was down as much as 0.8% on Monday, but rebounded in the afternoon to reclaim its 50-day moving average (2878.47), which it had breached shortly after the opening bell. The benchmark index finished just slightly lower, closing at 2884.43.

As for the other major averages, the tech-heavy Nasdaq Composite underperformed for the third straight day, losing 0.7%; the small-cap Russell 2000 finished the day with a slim loss of 0.2%; and the blue-chip Dow Jones Industrial Average outperformed, tacking on 0.2%.

Concerning headlines overseas weighed on U.S. markets early. In China, Secretary of State Mike Pompeo traded jabs with China's foreign minister, Wang Yi, regarding trade disputes. Mr. Yi accused the United States of meddling with domestic affairs, and Mr. Pompeo retorted that the two simply had a "fundamental disagreement." In Italy, the government continued its feud with the European Union over its budget deficit plan, with Italy's Deputy Minister Matteo Salvini referring to two EU leaders as "enemies of Europe."

The top-weighted information technology sector gave up quite a bit of ground on Monday, closing at the bottom of the S&P 500 sector standings with a loss of 1.2%. The group is now down 3.4% for the month, trimming its 2018 gain to 15.5%. Investors have continued to take profits from the highly-valued growth stocks that have helped propel the group higher this year.

Conversely, the real estate (+1.3%), consumer staples (+1.3%), and utilities (+0.8%) sectors finished atop Monday's leaderboard, and the highly-influential financial sector (+0.6%) also outperformed.

In corporate news, Google's parent company Alphabet (GOOG 1148.97, -8.38) announced that account information of 500,000 of its users was exposed due to a bug, and General Electric (GE 13.61, +0.43) was upgraded to 'Overweight' from 'Equal Weight' at Barclays. Alphabet shares lost 0.7%, while GE shares climbed 3.3%.

Looking head, the third quarter earnings season will unofficially kickoff on Friday with financial giants JPMorgan Chase (JPM 115.32, +0.70, +0.6%), Citigroup (C 72.59, +0.17, +0.2%), and Wells Fargo (WFC 53.67, +0.48, +0.9%) scheduled to report their quarterly results.

Note, the bond market was closed in observance of Columbus Day.

Investors did not receive any economic data on Monday.

• Nasdaq Composite +12.1% YTD
• S&P 500 +7.9% YTD
• Dow Jones Industrial Average +7.2% YTD
• Russell 2000 +6.1% YTD