You'd be wise to keep an eye out for monster stocks in the making, because they're the ones that can make you quite wealthy over time. All the giant companies of today have been monster stocks in the making.

Here are three candidates to consider for your portfolio. Each of them has much growth potential, and if they execute their strategies well, can deliver great rewards to long-term shareholders.

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1. Axon Enterprise

Axon Enterprise (AXON -1.23%) was founded in 1993 with a name you might know better -- Taser. It was initially focused on weapons, but now, with a new name, its offerings include body cameras and other technology that can be used to boost public safety. It bills itself as "a market-leading provider of law enforcement technology," with its mission "to protect life." The company notes that 48 major North American cities are using Axon cameras and software, and that its products and services have saved 254,367 lives.

So how is the business doing? Between 2016 and 2020, overall revenue has grown 26% on a compounded annual basis. Breaking that down into revenue-generating units, taser revenue has averaged 16%, while "sensors and other" has averaged 40% growth, and Axon cloud services has averaged 57%. (It's worth noting that its cloud offerings recently sported a hefty 77% gross margin.) Axon sees itself having a total addressable market of around $27 billion, and it's going after it. The company has great growth potential.

2. Etsy

If you like to shop online, especially for handmade and vintage items, you're probably familiar with Etsy (ETSY -1.75%). But you might not realize how big it is and how quickly it's growing. Etsy's second-quarter results reflect a company with more than 90 million active buyers (up 50% from the prior year) and more than 5.2 million sellers (up 67%).

Those rising numbers are evidence of a strengthening sustainable competitive advantage, as the online marketplace becomes where buyers will go to find sellers, and vice versa. Meanwhile, gross merchandise sales and total revenue grew by 13% and 23%, respectively, year over year -- and that's impressive, since a year earlier, business was booming due to millions buying masks online. Overall, its customers' engagement is growing, as they spend more at

But wait -- there's more! Etsy is also broadening its geographic and categoric scope, via acquisitions. It bought the online musical instrument marketplace Reverb in 2019, and more recently has snapped up the U.K.-based fashion resale marketplace Depop and the Brazilian artisan marketplace Elo7 (known to some as "the Etsy of Brazil"). (By the way, Brazil's population is around 214 million -- about 65% of the U.S.'s approximate 331 million.) Etsy appears to be a well-oiled growth machine.

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3. Coupang

Then there's Coupang (CPNG -0.73%), a huge and growing e-commerce business based in South Korea. It's expanding globally, and some expect it to dominate in Asia the way that dominates in the U.S. (and elsewhere) and MercadoLibre dominates in Latin America. That may be a tall order, since there's less room for growth in South Korea and it does have competition there, but the company is still likely to keep growing at a good clip.

The company's recently reported second quarter was its "15th consecutive quarter of over 50% constant-currency revenue growth," featuring revenue growth of 71% year over year and gross profit increasing by 86%. (Notably, the company has been posting net losses, not gains -- but many young and fast-growing companies do so, as they plow every available dollar into furthering their growth.)

Coupang, like Etsy, is also growing by introducing new services and tackling new regions. It has introduced grocery-delivery and restaurant-food-delivery services, and has introduced a subscription service like Amazon's Prime. These can be costly to get up and running, though, and can put pressure on profit margins. The company is also expanding in Japan, and eyeing Singapore, Taiwan, and Malaysia, too. It will face competition from existing e-commerce lions in those countries.

Each of these three companies holds much promise, and might reward you handsomely over the long term. Be sure to do your own digging into any of them that interest you, and pay attention to valuation. It can be worth paying a lot for some growth stocks, but if you pay too much, your overall long-term gain may suffer.