A "monster stock" might be one that frightens you by free-falling. Or it might alarm you with characteristics such as plummeting sales, shrinking profit margins, or surging debt. We'll use a different definition for this article.

We'll consider monster stocks to be ones that have actually performed very well and/or are likely to continue doing so. They'll be stocks with attractive qualities, such as market dominance, healthy balance sheets, and/or promising growth prospects -- ones you could aim to hold for a decade or more.

Got it? Great -- here, then, are five such "monster stocks" to consider for berths in your long-term portfolio.

Image source: Getty Inages.

1. The Trade Desk

The Trade Desk (TTD 3.71%) has been quite a market darling in the past. Its 15-year average annual return is close to 16%. It's been volatile, too -- over the past 12 months, its stock was recently down 44%. That kind of drop has made the stock attractive to long-term growth-oriented investors. For example, its recent forward-looking price-to-earnings (P/E) ratio of 43.8 is well below its five-year average of 88.5.

With a recent market value of $24 billion, The Trade Desk is a digital advertising giant, helping its customers program effective advertising campaigns online. As long as businesses want to advertise online, The Trade Desk is likely to do a lot of business. However, should we end up in a recession, that's when many companies cut back on their advertising. This would hurt The Trade Desk -- at least for a while.

2. Palo Alto Networks

Palo Alto Networks (PANW -1.25%) is a titan in the cybersecurity realm, with a recent market value of $111 billion. It's been a monster stock, averaging annual gains of more than 21% over the past decade -- and more than 40% over the past five years. Year to date, though, the stock was recently down 6.6%. Its forward P/E was recently 46.3, a bit below the five-year average of 52.5.

Is it worth buying? For risk-tolerant long-term investors, it's certainly worth a closer look. Anyone with a connected digital device should be concerned about security, and the need for cybersecurity services doesn't look like it's going away anytime soon. It has been transitioning customers to a simplified set of platforms recently, and that has been going well.

It's also incorporating artificial intelligence (AI) into its offerings and making its services cloud-based and subscription-based. Savvy investors love to see subscription services, as they provide more dependable recurring revenue.

3. Amazon.com

Amazon.com (AMZN -1.01%) is clearly a monster stock, having grown to a recent market value of nearly $2 trillion. There's a lot to love about Amazon beyond its massive online marketplace, such as its dominant Amazon Web Services (AWS), a cloud computing platform. It's true that the marketplace generates the most revenue, but that's relatively low-margin revenue. Its AWS and digital advertising operations, to name a few, are higher-margin enterprises.

If you're fearing a recession, it's true that that could hurt Amazon's retailing business -- as could tariffs. But Amazon is often viewed as a relatively low-cost seller, so its business might be more resilient than that of other retailers. Meanwhile, with a recent forward P/E ratio of 28 (well below its five-year average of 50), the stock seems attractively valued.

4. Coupang

Coupang (CPNG 0.68%) is not a household word in the U.S., but the company is a major and growing Amazon-like enterprise. Based in South Korea, it encompasses an online marketplace, restaurant delivery, video streaming, fintech (financial technology) offerings, and more.

Coupang has a strong balance sheet, and its gross profit has been growing by double digits -- by 29%, actually, year over year in its fourth quarter of 2024. Coupang has expanded into Taiwan, and revenue there grew by 23% quarter over quarter. Coupang's recent forward P/E ratio was only 16.2, which is compelling for a company growing as quickly as Coupang is growing.

5. CRISPR Therapeutics AG

CRISPR Therapeutics AG (CRSP -0.08%) is the fifth stock to consider, and arguably the most speculative of the bunch. It's a leader in gene editing technology, but gene editing is still in its early days. Meanwhile, biotechnology offerings take a lot of time to develop and bring to market -- if they ever make it that far. That said, CRISPR has a promising pipeline of treatments in development, and a partnership with Vertex Pharmaceuticals.

If you're intrigued, take a closer look at CRISPR -- and any other of these companies that interest you.