The AI rally has minted some unlikely heroes in the ETF world. Two leveraged funds tied to Micron Technology (MU)—the Direxion Daily MU Bull 2X Shares (MUU) and the GraniteShares 2x Long MU Daily ETF (MULL)—have delivered gains of around 800% so far in 2026. That makes them the best-performing U.S.-listed ETFs year to date, and it's not even close.
These funds are essentially turbocharged bets on Micron, which has become one of Wall Street's favorite AI plays thanks to its leadership in high-bandwidth memory (HBM), a critical component in the AI accelerators that power everything from ChatGPT to data center training clusters.
Why Micron Is on Fire
Micron's stock has been on a tear, and for good reason. The company's fiscal third-quarter results were a blockbuster: revenue hit $11.1 billion, up 37% year over year and ahead of Wall Street expectations. Adjusted earnings of $2.95 per share also topped estimates. Data center revenue more than doubled from a year earlier, driven by surging demand for HBM.
Management said HBM revenue has already surpassed its fiscal 2025 target, and they expect the market to remain supply-constrained through calendar 2026. Hyperscalers and cloud providers are spending heavily on AI infrastructure, and Micron is right in the middle of it. The AI memory boom, it seems, is still in its early innings.
The Magic (and Math) of Leveraged ETFs
So why have MUU and MULL gained so much more than Micron itself? The answer lies in how these products work. Unlike diversified semiconductor ETFs like the iShares Semiconductor ETF (SOXX), VanEck Semiconductor ETF (SMH), or State Street SPDR S&P Semiconductor ETF (XSD), MUU and MULL are single-stock leveraged ETFs. They aim to deliver twice (2x) the daily return of Micron shares.
Because they rebalance daily, sustained upward momentum in the underlying stock can produce returns that far exceed a simple 2x multiple over longer periods. Micron's persistent rally throughout 2026 has created the perfect environment for leveraged compounding. The result? Gains of more than 1,000% for some investors who got in early.
The surge has also attracted serious money. MUU crossed $1 billion in assets under management earlier this year, as traders piled into what is essentially a high-conviction bet on one of the market's hottest AI winners.
The Catch: Leverage Works Both Ways
Before you rush to buy MUU or MULL, it's worth understanding the risks. These ETFs are designed to achieve their target returns over a single trading day. They are tactical trading vehicles, not buy-and-hold investments. During periods of volatility or a sustained decline in Micron's stock, daily compounding can erode returns just as dramatically as it amplified them on the way up.
In other words, the same leverage that turned MUU and MULL into the standout ETF success stories of 2026 could just as easily turn them into cautionary tales. For now, though, Micron's AI-fueled momentum has made these funds the darlings of the ETF world—a reminder that concentrated exposure to a single hot stock can produce extraordinary gains, along with equally extraordinary risk.
