Energy is the best performing sector this year, after underperforming the broader market for many years. The Energy Select Sector SPDR Fund (XLE) has surged 41% in 2021.The rollout of coronavirus vaccines is accelerating and expected to bring an end to this deadly pandemic. Further, the massive $1.9 trillion fiscal stimulus is expected to boost US economic growth.Oil has also been rallying this year as Saudi Arabia had unexpectedly cut its production significantly to boost prices. Last week, oil prices jumped more than 4% after OPEC and its allies agreed to extend most of their production cuts through April.The OPEC expects oil demand to increase by 5.9 million barrels per day year-over-year in 2021, while the supply to be largely unchanged.The Vanguard Energy ETF (VDE) tracks a market cap weighted index of US energy companies. Exxon (XOM) and Chevron (CVX) account for almost 40% of the portfolio.The SPDR S&P Oil & Gas Exploration & Production ETF (XOP) is an equal-weighted ETF. It tilts away from the oil giants and toward small- and mid-cap companies.The VanEck Vectors Oil Services ETF (OIH) holds 25 largest US-listed oil services companies. Schlumberger (SLB) and Halliburton (HAL) are its top holdings.To learn more about these ETFs, please watch the short video above.Want key ETF info delivered straight to your inbox?Zacks’ free Fund Newsletter will brief you on top news and analysis, as well as top-performing ETFs, each week. Get it free >>Want the latest recommendations from Zacks Investment Research? Today, you can download 7 Best Stocks for the Next 30 Days. Click to get this free report Exxon Mobil Corporation (XOM): Free Stock Analysis Report Chevron Corporation (CVX): Free Stock Analysis Report Schlumberger Limited (SLB): Free Stock Analysis Report Halliburton Company (HAL): Free Stock Analysis Report VanEck Vectors Oil Services ETF (OIH): ETF Research Reports To read this article on Zacks.com click here. Zacks Investment Research Want the latest recommendations from Zacks Investment Research? Today, you can download 7 Best Stocks for the Next 30 Days. Click to get this free report