Advanced Micro Devices AMD) and Meta Platforms META) were two of Monday’s biggest mega-cap winners, with both stocks surging roughly 10% as enthusiasm around artificial intelligence returned in force.

AMD reached a $1 trillion market-cap threshold for the first time, joining Meta in the exclusive trillion-dollar club, as investors piled back into AI-related semiconductor stocks. (*The chart below is from Friday, September 18).

Meta’s rally, meanwhile, was fueled by excitement surrounding its new Muse AI assistant, which has quickly climbed to the top of Apple’s AAPL) U.S. App Store.

AMD’s AI Rally Reaches a New Milestone

AMD’s surge reflects growing confidence that the chipmaker can capture a larger portion of the booming AI-compute market alongside Nvidia NVDA). Beyond its Instinct AI accelerators, AMD is benefiting from strengthening demand for server CPUs, which play an important role in AI inference and agentic workloads.

That narrative received another boost from the rapid adoption of Meta’s Muse. To that point, more capable AI agents could require substantially greater CPU resources, potentially expanding the addressable market for AMD’s EPYC server processors.

AMD has also been accelerating its AI product cadence and expanding from individual chips toward more complete data-center systems.

Still, after a massive run this year (+180% YTD) and today’s jump to record highs of over $600 a share, much of that optimism is increasingly reflected in AMD stock.

Meta’s Muse Gives Investors Another AI Growth Catalyst

Meta’s rally has a more company-specific catalyst. Muse, launched earlier this month, quickly became the top free app in Apple’s U.S. App Store, strengthening hopes that Meta can turn its enormous AI spending into new consumer products and eventually additional revenue streams.

Meta Muse is a personal AI agent—essentially a more autonomous version of a chatbot that can take actions on a user’s behalf. Through the Muse app or WhatsApp, it can handle tasks such as sending emails, booking travel, filling out forms, making reservations, and shopping online.

The enthusiasm is particularly meaningful because Meta has faced persistent questions over whether its enormous AI infrastructure investments will generate adequate returns. Muse's early traction gives investors a tangible example of how that spending could extend Meta beyond its core advertising business.

Although AMD offers the faster growth trajectory, Meta stock trades at a much more reasonable 23X forward earnings multiple. Still, Meta shares have faced pressure this year amid rising costs and heavy capital spending.

Bottom Line

AMD and Meta remain two compelling long-term participants in the AI boom, but chasing such sizable one-day rallies may not be necessary.

Notably, AMD and META stock both currently land a Zacks Rank #3 (Hold), suggesting investors may be better served waiting for more attractive entry points following today’s sharp advances.

Beyond Nvidia: AI's Second Wave Is Here

The AI revolution has already minted millionaires. But the stocks everyone knows about aren't likely to keep delivering the biggest profits. AI’s second wave is moving from infrastructure to implementation and these companies are at the forefront of this transition, positioned to become what Amazon and Google were to the internet era.

Advanced Micro Devices, Inc. (AMD) : Free Stock Analysis Report

Meta Platforms, Inc. (META) : Free Stock Analysis Report

Apple Inc. (AAPL) : Free Stock Analysis Report

NVIDIA Corporation (NVDA) : Free Stock Analysis Report

This article originally published on Zacks Investment Research (zacks.com).