The rollout of the $1.9 trillion fiscal support from the Biden administration, growing distribution of vaccines and the starting of economic reopening were the key highlights of the first quarter of 2021. However, the quarter also faced some concerns while closing out as COVID-cases have started rising globally.There were some disbalances in the financial markets too in the quarter in the form of Reddit Frenzy (that made stocks like GameStop a star overnight) and Archegos’ default on margin call and the resultant selling of its holdings by some renowned banks (read: Marijuana ETFs on a High on Reddit Frenzy).Rising rate worries and fears of a tax rate hike in the United States also dampened investors’ sentiments in March. The benchmark U.S. treasury yield went up to 1.73% on Mar 29, 2021 from 0.93% at the start of the year. Overall, the S&P 500 Index, the Dow Jones, the Nasdaq and the Russell 2000 gained about 6.2%, 9%, 1.5% and 12.1%, respectively, in the quarter (as of Mar 30, 2021).Against this backdrop, let’s see which ETFs raked in solid assets and the ones that lost.S&P 500 & Total Market ETFs Were FavoritesVanguard S&P 500 ETF VOO and iShares Core S&P 500 ETF IVV amassed about$17.05 billion and $8.09 billion in assets, respectively. Vanguard Total Stock Market ETF (VTI) also garnered about $9.12 billion in assets. Though still not out of woods, the U.S. economy is showing signs of improvement. Hence, investors bet big on the broader market.Financials Gained TooA steepening yield curve, undervaluation, decent earnings growth potential and Fed's decision to okay shareholder value maximization if stress test is cleared are some of the factors that made bank ETFs well positioned (read: 4 Sector ETFs to Watch for Gains in Q2).With the Fed being dovish and economic improvements boosting long-term yields, the yield curve has steepened this year. The biggest winner of the steepening yield curve is the financial sector. As banks seek to borrow money at short-term rates and lend at long-term rates, banks earn more on lending and pay less on deposits amid a steepening yield curve, thereby leading to a wider spread. This expands net margins and increases banks’ profits. Financial Select Sector SPDR Fund XLF has attracted about $8.97 billion in assets.Emerging Markets: A Winner TooiShares Core MSCI Emerging Markets ETF IEMG added about $7.43 billion in the quarter despite the strength of the greenback. Some emerging economies enacted rate hikes in the quarter, which probably boosted investors’ optimism in those markets. Vaccine distribution was another positive.ARK Innovation Wins Despite Depletion in ReturnGrowth-focusedARK Innovation ETF ARKK, which has been a pandemic winner, gained assets too. Focus on high-flying Tesla benefited the fund last year. Though the fund has underperformed this year, investors seem to have solid faith in it and continue to pour out assets (read: Are You a Fan of Ark ETFs' Cathie Wood? Follow This Portfolio).Gold Loses Its GlitterSPDR Gold Trust GLD has lost about $7.52 billion in assets as this safe-haven asset fell out of favor amid risk-on trade sentiments.High-Yield Bond ETFs Fall Flat TooAs treasury yields started rising in the quarter, investors turned their face from the higher-yield but riskier bets.iShares iBoxx USD Investment Grade Corporate Bond ETF LQD, iShares iBoxx USD High Yield Corporate Bond ETF HYG and SPDR Bloomberg Barclays High Yield Bond ETF (JNK) lost about $10.8 billion, $4.6 billion and $2.37 billion in assets, respectively, in the quarter.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 Financial Select Sector SPDR ETF (XLF): ETF Research Reports SPDR Gold Shares (GLD): ETF Research Reports iShares iBoxx High Yield Corporate Bond ETF (HYG): ETF Research Reports iShares iBoxx Investment Grade Corporate Bond ETF (LQD): ETF Research Reports iShares Core S&P 500 ETF (IVV): 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