Stock Market Today, July 21: Micron Surges 12% as Semiconductor Strength Lifts Nasdaq

Micron jumped 12% on July 21, 2026, leading a semiconductor rally that pushed the Nasdaq up 1.29%. The S&P 500 gained 0.89% and the Dow Jones added 0.74%. SanDisk soared 14%, while AMD climbed 8% following an AI deal with Microsoft. General Motors and AeroVironment also posted gains.

The chip surge came despite ongoing geopolitical tensions and tariff concerns, driven by strong AI demand from South Korea. The semiconductor strength extended beyond memory and GPU makers, with the rally lifting broader market indices as investors rotated into tech on AI infrastructure tailwinds.

AMD's Microsoft partnership added fuel to the AI theme, reinforcing the narrative that enterprise spending on artificial intelligence remains robust. The rally suggests traders are looking through macro headwinds to focus on sector-specific catalysts in semiconductors.