Gains in technology and communications stocks helped outweigh losses in consumer goods companies and elsewhere in the market.
Semiconductor giant Nvidia, whose enormous valuation gives it an outsize influence on indexes, rose 3.6%. Broadcom jumped 5.7% to also help support the broader market.
Walmart fell 2.2% and PepsiCo slid 1.3%.
Japanese automakers Honda Motor and Nissan said they are talking about combining in a deal that might also include Mitsubishi Motors. U.S.-listed shares in Honda jumped 12.1% , while Nissan fell 0.9%.
Eli Lilly rose 3.3% after announcing that regulators approved Zepbound as the first and only prescription medicine for adults with sleep apnea.
Department store Nordstrom fell 1.7% after it agreed to be taken private by Nordstrom family members and a Mexican retail group in a $6.25 billion deal.
The Conference Board said that consumer confidence slipped in December. Its consumer confidence index fell back to 104.7 from 112.8 in November. Wall Street was expecting a reading of 113.8.
The unexpectedly weak consumer confidence update follows several generally strong economic reports last week. One report showed the overall economy grew at a 3.1% annualized rate during the summer, faster than earlier thought. The latest report on unemployment benefit applications showed that the job market remains solid.
A report on Friday said a measure of inflation the Federal Reserve likes to use was slightly lower last month than economists expected. Worries about inflation edging higher again had been weighing on Wall Street and the Fed.
The central bank just delivered its third cut to interest rates this year, but inflation has been hovering stubbornly above its target of 2%. It has signaled that it could deliver fewer cuts to interest rates next year than it earlier anticipated because of concerns over inflation.
Expectations for more interest rate cuts have helped drive a 25% gain for the S&P 500 in 2024. That drive included 57 all-time highs this year.
Inflation concerns have added to uncertainties heading into 2025, which include the labor market's path ahead and shifting economic policies under an incoming President Donald Trump.
"Put simply, much of the strong market performance prior to last week was driven by expectations that a best-case scenario was the base case for 2025," said Brent Schutte, chief investment officer at Northwestern Mutual Wealth Management Company
Treasury yields rose in the bond market. The yield on the 10-year Treasury rose to 4.59% from 4.53% late Friday.
European markets were mostly lower, while markets in Asia gained ground.
Wall Street has several other economic reports to look forward to this week. On Tuesday, the U.S. will release its November report for sales of newly constructed homes. A weekly update on unemployment benefits is expected on Thursday.
Markets in the U.S. will close at 1 p.m. Eastern on Tuesday for Christmas Eve and will remain closed on Wednesday for Christmas.