The S&P 500 advanced more than 2 percent, as financials, industrials and health care led all sectors higher, and snapped a nine-day losing streak, its longest since December 1980. The Nasdaq composite outperformed, rising 2.4 percent. The three major indexes also posted their best day since March 1.

"This is mostly a political-relief rally. The market tends to favor a divided-control scenario [in government] and this raises those odds," said Bruce McCain, chief investment strategist at Key Private Bank. "This is a week to settle out the election and then we'll see where investors turn their attention to."

The Dow Jones industrial average rose approximately 370 points, with Goldman Sachs and UnitedHealth contributing the most gains to the tune of 35 points and 27 points, respectively.

"Assuming the election is as expected, ... I think investors will pivot to the Fed," Sonders said. "That said, if it's a Trump win, the market will continue to focus on that."

Financial markets in the U.S. and around the world had been largely pricing in a victory for Clinton over Republican nominee, Donald Trump . Market expectations for Congress, meanwhile, had been for the House to remain under GOP control while the Senate flips in favor of the Democrats.

"The likelihood of [a split government] is now higher, but you also had the market down for nine days in a row, so you're also getting a rubber-band effect," said Liz Ann Sonders, chief investment strategist at Charles Schwab.

U.S. equities kicked off the week on a high note, closing sharply higher on Monday after the FBI again cleared Democratic nominee Hillary Clinton over her use of a private server.

"In terms of the market and its possible response on Wednesday, today's reaction to the FBI news is obvious evidence that market participants have wrapped up the world in a nice and easy box," said Peter Boockvar, chief market analyst at The Lindsey Group.



"Hillary wins, good for stocks. Trump wins, bad for stocks. But, anyone who thinks deeper than this knows that the response is going to be much more nuanced. Ask any owner of a healthcare, financial or defense stock," he said in a note.

Naeem Aslam, chief market analyst at Think Markets, said in a note investors should also watch out for any surprises. "Donald Trump's victory will not only bring the knee jerk reaction for the market, but we are also concerned about the geopolitical uncertainty," he said.

In a letter sent to Congress on Sunday, FBI Director James Comey said the bureau had "not changed its conclusions," reached in July, on Clinton's private email server. This new investigation, which came to light on October 28, kept financial markets across the globe on edge.

Entering Monday, the S&P had fallen more than 2 percent since the new probe was announced. The Mexican peso, considered a proxy trade for the U.S. election — which will be held on Tuesday — had fallen as much as 3.89 percent since October 28. Since then, Clinton's lead in the polls overTrump has narrowed significantly, according to data from RealClearPolitics.



"From everything I've read, it seems like Clinton's winning by about 2 percent, ... but there is a concern out there that the polls are not correct, and that they underestimate the number of Trump supporters," said Thomas Wilson, senior investment manager at Brinker Capital.

But the Mexican currency popped around 2 percent against the greenback Monday to trade near 18.653. Mexican stocks also ripped higher, as the iShares MSCI Mexico Capped ETF (EWW) gained 5.4 percent, on posting its largest one-day percentage increase since 2011.

The U.S. dollar also rose broadly against a basket of currencies, with the euro near $1.104 and the around 104.5.

Other asset classes also saw significant moves, as investors unloaded previous risk-off positions. U.S. Treasurys fell, with the two-year note yield near 0.81 percent and the benchmark 10-year yield around 1.82 percent.

Gold futures for December delivery also fell, settling $25.10 lower at $1,279.40 per ounce. Meanwhile, the CBOE Volatility Index (VIX), widely considered the best gauge of fear in the market, fell 16.2 percent lower, near 18.87, and snapped a nine-day winning streak.

S&P (blue) vs gold futures (green) intraday

Source: FactSet

Separately, in an interview with CNBC's "Squawk Box," Appaloosa Management founder David Tepper said Monday he has become more bullish on stocks in the past few weeks after generally being "pretty cautious on the market, not outright bearish."



In oil markets, U.S. crude gained 1.86 percent to settle at $44.89 per barrel, boosted by a commitment from OPEC to stick to a deal to cut output, but prices remained more than $7 below last month's high due to persistent doubts over the feasibility of the group's plan.

