U.S. stocks on Monday had their best day since March on a percentage basis after the Federal Bureau of Investigation said its review of a new batch of Democratic presidential nominee Hillary Clinton’s emails won’t lead to charges.

Gains were broad, with the Dow Jones Industrial Average reclaiming the key 18,000 level and the S&P 500 snapping its nine-day losing streak, the longest since 1980. The slide had been attributed partly to polls showing a closer contest between Clinton and Republican rival Donald Trump.

Read: What happens after the S&P 500 falls 9 days in a row?

The Dow Jones Industrial Average DJIA, -0.84% soared 371.32 points, or 2.1%, to close at 18,259.60. The Dow’s rally marks its best session before a presidential election since Nov. 7, 1932, when the blue chip index rose 3.5%, according to Dow Jones data.

The S&P 500 index SPX, -1.15% rose 46.34 points, or 2.2%, to finish at 2,131.52. The Nasdaq Composite Index COMP, -1.73% climbed 119.80 points, or 2.4%, to end at 5,166.17.

See:Will the Clinton relief rally for stocks last? What analysts say

FBI Director James Comey informed lawmakers on Sunday that there were no new findings in the additional emails discovered on the computer of former Rep. Anthony Weiner, whose estranged wife is Clinton aide Huma Abedin. News that the FBI had discovered the new batch of emails just over a week ago jolted the presidential election race, taking a toll on Clinton’s lead in polls.

FBI: New emails don’t change decision on Hillary Clinton

“The rally is all about Clinton having a better chance of winning, though I don’t think the market is celebrating her policies so much as reflecting how markets, like many Americans, are fearful of the unknown that comes with Trump,” said James Meyer, chief investment officer at Tower Bridge Advisors.

Read: These 5 charts show the global relief rally after FBI clears Clinton — again

Financial markets in general view a Clinton win as the better outcome in Tuesday’s election, as it presents fewer unknowns and possibly more stability for markets than a Trump presidency.

While the day’s gains were broad, financials were the biggest advancers. The S&P financial index popped 2.6%, boosted by a 3.2% rise in shares of Goldman Sachs Group Inc. GS, -1.61% . J.P. Morgan Chase & Co. JPM, -0.71% climbed 3.1% to $69.88.

Read: Here are all possible election outcomes — and how markets will react

Despite the rally, the election could remain an overhang of uncertainty until a winner is decided. Investors are also paying close attention to what party will control the House of Representatives and Senate.

See:An unclear election result would be worst outcome for stocks

“How markets will perform from today’s open through tomorrow’s close is anybody’s bet,” said Meyer. “To the extent Clinton’s probability of winning changes, the market will change with it.”

But for all the alarming headlines and the market’s whiplash swings, Kent Engelke, chief economic strategist at Capitol Securities Management Inc., believes the Clinton-Trump contest pales in comparison to previous elections.

“Regardless of the outcome the country will survive,” he said in emailed comments. “All must remember democracy is an angry visceral process filled with vitriol and animosity. Democracy settles its differences with words versus guns.”

A revival in appetite for riskier assets triggered a global equity rally, with European stocks up more than 1%. In Asia, the Nikkei 225 index NIK, -0.05% soared 1.6% as the Japanese yen USDJPY, +0.43% fell against the dollar. The yen and gold are seen as assets that investors turn to in times of economic and political uncertainty.

Read:How the stock market tends to perform on and after Election Day

Gold US:GCZ6 was down sharply, after gaining 2.2% last week on a boost in the polls for Trump. Oil CLZ26, -1.13% rose more than 1%.

The dollar saw big gains, with the ICE Dollar Index DXY, +0.23% , which measures the greenback against a half-dozen rivals, up 0.7%.

The Mexican peso USDMXN, +2.63% traded at $18.61 to the dollar, versus $19.02 earlier in Asia ahead of the FBI headlines. Many believe a Trump victory would harm the Mexican economy as the candidate has repeatedly promised to raise trade barriers and build a wall on the U.S.-Mexican border.

On the corporate front, third-quarter earnings are trending ahead of Wall Street’s estimates. With 88% of S&P 500 companies having announced results, third-quarter earnings are coming in 4% better than analysts’ projections, the biggest beat since the second quarter of 2015, according to Savita Subramanian, equity and quant strategist at Bank of America Merrill Lynch.

Stocks to Watch: Shares of Warren Buffett’s Berkshire Hathaway Inc. BRK.A, -0.64% BRK.B, -1.00% rose more than 2% after the multinational conglomerate posted results late Friday.

Read:Cash at Buffett’s Berkshire Hathaway hits record with stock market near highs

Shares of LendingClub Corp. LC, -5.40% jumped 15% after results of the online credit marketplace beat forecasts.

Auction house Sotheby’s US:BID posted a wider-than-expected loss, but revenue beat forecasts, sending shares up 11%.

--Barbara Kollmeyer contributed to this article.