Meta's stock has rallied sharply in September 2026 on sustained AI momentum, including expanded Llama model releases, the Muse AI initiative, and heavy data-center spending that analysts link to both capability gains and potential tax advantages. Traders are watching advertising revenue trends and whether these investments translate into measurable user engagement or monetization lifts across Instagram, WhatsApp, and the Meta AI chatbot. With Q3 earnings expected in late October, guidance on AI ROI and capital expenditures will likely set the tone for the final trading sessions of the month. Broader tech-sector sentiment and any regulatory updates on AI infrastructure also remain swing factors.