"Overall, there was a lot of negativity surrounding biotechs. We got some positive data from some of the small and midcap companies and that's boosting the [IBB]," said Mike Bailey, director of research at FBB Capital Partners.
"I think we're still sort of in between catalysts," he said. "I think the market is up today on a lack of negative catalysts and some soft, positive catalysts." Bailey added the next major catalyst for stocks will be earnings season, which is set to begin this week.
U.S. crude rose 3.1 percent to settle at $51.35 per barrel while Brent futures hit a one-year high after Russian President Vladimir Putin said Russia is ready to join a proposed cap on oil output by OPEC members.
Putin, speaking at an energy congress in the Turkish city of Istanbul, said he hoped that OPEC members would confirm the decision to adopt quotas for output when the organization meets in November.
"This has removed the uncertainty and now we are in clear," said Naeem Aslam, chief market analyst at Think Markets, in a morning note. "However, it is important to keep in mind that unless we see the planned action complete, caution may be the best practice. If history tells us anything, it is this that these major oil players also have habit to not to respect the agreed agreement."
Investors were also keeping an eye on the U.S. presidential election.
Donald Trump and Hillary Clinton squared off in a town hall-style debate Sunday night in St. Louis. Trump, in particular, largely stuck to personal attacks, threatening at one point that he would "get a special prosecutor" to look into Clinton's handling of classified information if he were elected president.
"I would have to agree that the market is taking at [a tie]," said Peter Cardillo, chief market economist at First Standard Financial. "If the market had thought that Trump had gotten a positive gain, we wouldn't be higher."
U.S. stock futures traded higher before the opening bell, with Dow futures rising more than 100 points, while S&P and Nasdaq futures gained 11.75 points and 24.25 points, respectively. Still, Cardillo said trading volume was likely to be light on Monday, given the Columbus Day holiday during which U.S. banks were closed.
The Mexican peso shot about 2 percent higher against the dollar on Monday. The dollar-Mexican peso trade has been a proxy trade during the election, given Trump's desire to build a wall along the Mexican border and call to go as far as withdrawing the U.S. from NAFTA if he were elected.
Trump "had a better evening compared to his previous showdown with the former Secretary of State, yet all polls currently suggest that the Democrat will be the one to pack her bags for the White House," said Jeremy Klein, chief market strategist at FBN Securities.
Trump's campaign has been under fire recently, after a leaked 2005 video of the GOP standard bearer's vulgar remarks about women caused uproar.
US dollar/Mexican peso in 2016