Wall Street was upbeat last week with the S&P 500, the Dow Jones and the Nasdaq adding about 3.5%, 2.6% and 6%, respectively. Gradual opening of economies, improvement in the virus outlook, developments in treatments and vaccines, the Fed and the U.S. government’s massive stimulus, and some upbeat earnings results for the first quarter aided the market rally. Against this backdrop, below we highlight a few ETF areas that won big time last week.EnergyAfter crashing in mid-April, pol prices recovered in May on an improved demand outlook based on the reopening of economies. United States Gasoline Fund (UGA) (up 24.2%), United States Brent Oil Fund BNO (up 15.9%) and U.S. Oil Fund LP (USO) (up 13.8%) are the toppers in this segment (read: Oil Price Rebound, USO ETF & More).Cloud ComputingSocial distancing norms enacted globally to mitigate the spread of the virus compelled people to stay as well as work and learn from home. This new lifestyle has boosted various corners of the technology sector, most importantly cloud computing (read: ETFs to Gain on Cloud Computing Growth Amid Coronavirus Crisis).Even before the lockdowns, companies were already discarding their own data centers to remain cost effective. This model benefited mega cloud owners like Amazon (AMZN), Microsoft (MSFT) and Google (GOOGL). And the latest coronavirus outbreak boosted the demand for clouds even more. As a result, WisdomTree Cloud Computing Fund (WCLD) (up 15.7%) benefited hugely.Online Retail Online shopping for groceries, food and essential items has become a mainstream in most parts of the globe amid lockdowns. In fact, non-store retail sales in March increased 12% year over year, up from 8.6% for the same month in 2019, per digitalcommerce360.com. Growth in the non-store channel made up more than half of all retail gains in March. The winning momentum was rife in April too. Amplify Online Retail ETF (IBUY) (up 15.6%) and Franklin Disruptive Commerce ETF BUYZ (up 14.1%) thus won big time (read: 5 Top-Performing ETF Areas of April That Are Up At Least 25%).ArgentinaEmerging markets staged a relief rally last week on cues of easing U.S.-China trade tensions. Beijing said Sino-U.S. trade negotiators had agreed to pace up the implementation of a Phase 1 deal, days after President Donald Trump threatened to impose new tariffs due to China’s apparent mishandling of the coronavirus outbreak.However, Argentina missed a deadline to reach an agreement with international creditors to restructure its $65 billion debt, but negotiations will continue. The three main bondholder groups have rejected a government restructuring proposal.iShares MSCI Argentina and Global Exposure ETF AGT (up 14.2%) and Global X MSCI Argentina ETF ARGT (up 13.7%) are two of the wining ETFs.BiotechHealthcare and biotech stocks and ETFs soared amid the ongoing medical emergency. Large pharma and biotech companies are working on medicines, vaccines and testing kits. Most recently, Gilead (GILD) indicated that the trial for coronavirus treatment Remdesivir has met its initial goal. And Remdesivir received the FDA nod for emergency use of coronavirus as an experimental drug. Moderna Inc. (MRNA), which is developing experimental vaccines, said it has entered into an agreement to manufacture a billion doses a year. This optimism kept Wall Street charged up. Virtus LifeSci Biotech Clinical (BBC) (up 13.8%) thus won last week.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 United States Oil ETF (USO): ETF Research Reports United States Brent Oil ETF (BNO): ETF Research Reports United States Gasoline ETF (UGA): ETF Research Reports Amplify Online Retail ETF (IBUY): ETF Research Reports Virtus LifeSci Biotech Clinical Trials ETF (BBC): ETF Research Reports Global X MSCI Argentina ETF (ARGT): ETF Research Reports iShares MSCI Argentina and Global Exposure ETF (AGT): ETF Research Reports Franklin Disruptive Commerce ETF (BUYZ): ETF Research Reports WisdomTree Cloud Computing ETF (WCLD): 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