The S&P 500 Momentum Index has surged 32% over the past two months, marking its best performance ever. This unprecedented rise was largely driven by mega-cap AI stocks, which propelled the index to a 19.3% gain in April alone, the strongest month on record for the momentum gauge. The Nasdaq Composite also experienced a significant boost, climbing 25% during April and May 2026, its best two-month performance since 2002. The S&P 500 added over $9.5 trillion in market capitalization recently, achieving 14 record highs in a single month. This surge in AI-related stocks created favorable conditions for momentum strategies, with Goldman Sachs' Momentum Factor climbing 25% over three months. Hedge fund exposure to momentum trades is nearing five-year highs, while the MSCI global momentum index outperformed the MSCI All Country World Index by 17 percentage points since March 2026. However, historical patterns suggest caution, as sharp momentum bursts near all-time highs often lead to short-lived peaks. Goldman Sachs notes that median forward returns over the next one to three months have historically been close to zero. This dynamic is crucial for crypto investors, as risk appetite in traditional markets influences capital flows into digital assets, with correlations between crypto and tech-heavy indices spiking during such regime changes.