Cathie Wood's Ark Invest does things a little differently than most exchange-traded fund (ETF) and mutual fund managers. Every day, Wood publishes the stocks Ark bought and sold for each of its funds in the previous day's session, giving investors a lot of insight into what she and her team see as the biggest opportunities.

While there have been dozens of stock purchases and sales in Ark's ETF portfolios so far this month alone, two recent buys stand out for their opportunities and ambitions in the rapidly evolving metaverse and artificial intelligence (AI) industries. Here's what they are and why they could be big winners if they can execute on their respective visions.

The most promising metaverse stock in the market

Wood recently added to the Ark Innovation ETF's (ARKK 1.05%) position in gaming platform Roblox (RBLX 1.35%) -- that stock now makes up about 3% of the ETF's portfolio. However, calling Roblox a gaming platform doesn't really do it justice. There are 65 million active users on the platform, and over 4 million developers earned money on Roblox in 2022. 

Roblox's business model mostly derives its revenue from in-app purchases. Users buy its Robux virtual currency, and this can be exchanged for a variety of features, access to content, and more. Roblox gets a share of all the revenue generated. It also sells premium subscriptions and has an advertising platform that is in the early stages, but is extremely promising.

Even in this challenging growth environment, Roblox has been delivering impressive results, with bookings up by 22% year over year in the second quarter. As more immersive wearable technology rolls out, such as virtual and augmented reality headsets announced by Apple (NASDAQ: AAPL), Roblox could benefit from a long-tailed growth tailwind. Metaverse technology is in its early stages, and the company wants to eventually bring 1 billion people on its platform. If it does that, it's fair to say that it could be a home run for investors.

The "other" AI chip stock

Wood recently bought shares of chipmaker AMD (AMD 2.37%) for the Ark Autonomous Technology & Robotics ETF (ARKQ 2.52%), and with all of the hype surrounding artificial intelligence, it isn't hard to see why. For the time being, AMD is a relatively small position (0.6%) in the fund, but it wouldn't be a big surprise if Wood and her team continued to build it.

AMD makes several types of chips, including central processing units (CPUs), data processing chips, and perhaps most exciting, graphics processing units, or GPUs.

Now, many people think of the GPU business as "Nvidia (NASDAQ: NVDA) and everyone else." And to be fair, Nvidia has a dominant share of that industry. But it's important not to ignore AMD. The company is developing a line of products designed with AI applications in mind, including its new Instinct MI300X GPU, which it intends to go head-to-head with Nvidia in the data center GPU space, which the latter has a 95% share of.

Not only could AMD take some of Nvidia's market share, but the market itself for AI-optimized chips is growing rapidly. If it's successful in capturing a larger piece of that expanding opportunity, AMD could be a big winner for its shareholders.

Both companies need a lot to go right

To be perfectly clear, a lot of things would have to go right in order for Roblox to reach 1 billion users on its platform (about 15 times its current user base), or for AMD to become a major player in the GPU space. There's a lot of execution risk with both investments, and even if management gets everything right, investors should expect some turbulence along the way. Neither of these is a low-risk investment, and both should be closely watched over the next few years while the metaverse and AI industries evolve.