The S&P 500 posted a slim gain on Monday as Treasury yields came off their highs and investors sought to look past Moody's downgrade of the United States' credit rating.

The benchmark added 0.09% and closed at 5,963.60, marking its sixth consecutive winning session. The Nasdaq Composite inched up 0.02% to end at 19,215.46. The Dow Jones Industrial Average rose 137.33 points, or 0.32%, and settled at 42,792.07. The 30-stock index was aided by a rebound in UnitedHealth, which saw an 8% jump after a recent bout of hard selling.

Treasury yields spiked after Moody's lowered the U.S. credit rating down one notch to Aa1 from Aaa, bringing the agency in line with peers. The firm cited financing challenges tied to the federal government's growing budget deficit and the ramifications of rolling over existing U.S. debts in a period of high borrowing costs.

The debt downgrade pressured bond prices and sent yields higher at a time when the economy is already awaiting the full impact of President Donald Trump's unfolding tariff policy. At their session highs, the 30-year U.S. bond yield jumped above 5% on Monday and the 10-year yield topped 4.5%, levels that hurt equity markets last month and helped lead Trump to back off his stiffest tariff measures. Rates on mortgages track the 10-year yield.

At their session lows on Monday, the Dow was off more than 300 points and the S&P 500 slipped about 1%. However, the major averages pared their losses as Treasury yields retreated from their highs.

"The Moody's report didn't highlight anything that every investor doesn't already know about the U.S. fiscal situation," said Ross Mayfield, investment analyst at Baird. "To me, it just kind of provided a little bit of cover for the market to take a breather here, but nothing that structurally changes our bullishness on where we think we'll be in the next six to 12 months."

Traders now see more trade deals as key to keeping the stock market comeback going, if higher yields don't scare away investors first.