Millennials, meaning people are currently between their mid-20s and late-30s, are often portrayed as a fickle generation with short attention spans. Former McDonald's CEO Steve Easterbrook, for example, once declared millennials were "promiscuous in their brand loyalty."

But if we take a closer look at the millennial market, we can still find plenty of companies that have locked in that fickle generation. Let's examine three high-growth players that fit that bill, and why their stocks could still have plenty of room to run.

1. The social media platform: Snap

Snap's (NYSE:SNAP) Snapchat is often associated with Gen Z, but millennials also account for a large percentage of the social media app's users. In 2018, The Manifest claimed 53% of millennials checked Snapchat daily, compared to 18% of Generation X users and 7% of baby boomers.

A group of smiling young adults taking a photo outdoors.

Image source: Getty Images.

During Snap's latest conference call, CEO Evan Spiegel claimed Snapchat reached "over 90% of the Gen Z population, and 75% of the Gen Z and millennial population, in countries like the U.S., the U.K., and France." Snapchat's popularity with those younger users enabled it to continue expanding, even as Facebook's Instagram aggressively cloned its features.

Snap's daily active users grew 18% year over year to 249 million last quarter, its average revenue per user rose 28%, and its total revenue surged 52% to $679 million -- marking its strongest year-over-year growth in over two years. It also narrowed its GAAP loss and posted an adjusted EBITDA profit.

Wall Street expects Snap's revenue to rise 42% this year and 41% next year. It's also expected to post a narrower loss and its first full-year non-GAAP profit in 2021. Snap's stock has already rallied 150% this year and isn't cheap at 18 times next year's sales -- but its popularity with younger users, its expanding ecosystem of videos, games, and filters, and its improving profitability all justify that premium valuation.

2. The online dating platform: Match

Match Group's (NASDAQ:MTCH) Tinder was the highest-grossing mobile app of 2019, according to App Annie. Two years ago, a Piper Jaffray survey found that 27% of single millennials used Tinder as their main dating app. Its closest competitor, Bumble, only held a 12% share.

Tinder's growth accelerated after it launched Tinder Plus in 2015 and Tinder Gold in 2017. Plus, which costs $10 per month for younger users in most markets, allowed users to undo swipes, swipe overseas, use "super likes" to get a user's attention, and temporarily "boost" the visibility of their profiles.

A smartphone user uses a dating app.

Image source: Getty Images.

Gold, an upgrade for Plus that costs an extra $5 a month, added curated "top picks" and the ability to see which users liked them right away. Last year, Match claimed over 70% of Tinder's users had upgraded to its Gold tier.

Match's revenue rose 18% year over year last quarter, with 15% growth in Tinder's direct (non-advertising) revenue and 23% growth in direct revenue from its other dating apps. Its total number of subscribers grew 12% year over year to 10.8 million as Tinder's subscribers rose 16% to 6.6 million, and its adjusted EBITDA increased by 21%.

Analysts expect Match's revenue and earnings to rise 15% and 9%, respectively, this year. Next year, they expect its revenue to grow 18% and its earnings to rise 23%. Match's stock already rallied 70% this year and isn't cheap at nearly 50 times forward earnings -- but its dominance of the online dating market arguably justifies that higher multiple.

3. The e-commerce platform: Etsy

Last year, a survey by Faire and The Harris Poll found that 37% of millennial women in the U.S. favored handmade gifts over mass-produced products, and 65% of all millennial shoppers preferred to buy holiday gifts from independent retailers instead of big retailers.

Those trends are pulling shoppers from Amazon toward Etsy (NASDAQ:ETSY), the leading marketplace for handmade products. Amazon challenged Etsy with its Handmade marketplace over the past few years, but Etsy's first-mover's advantage, lower seller fees, and more relaxed rules regarding sellers' promotional tools held Amazon at bay.

Etsy has consistently generated double-digit revenue growth since its IPO five years ago, and its revenue growth accelerated to triple-digit levels over the past two quarters as the pandemic sparked more online purchases. Its takeover of the online musical instrument marketplace Reverb last August also amplified those gains as brick-and-mortar stores shut down.

Etsy expects that feverish growth to decelerate in the fourth quarter, but analysts still expect its revenue and earnings to rise 97% and 175%, respectively, for the full year. Next year, they expect its revenue to rise 12% with 3% earnings growth after it laps the pandemic and its purchase of Reverb.

Etsy's stock has already rallied 220% this year and it trades at nearly 60 times forward earnings. That valuation is a bit frothy, but Etsy's dominance of the handmade niche, its resilience against Amazon, and its popularity with millennials should all support that higher P/E ratio.

This article represents the opinion of the writer, who may disagree with the “official” recommendation position of a Motley Fool premium advisory service. We’re motley! Questioning an investing thesis -- even one of our own -- helps us all think critically about investing and make decisions that help us become smarter, happier, and richer.