The year is more than half over, and investors have already had plenty of twists and turns and excitement to process. The S&P 500 is up roughly 15% across 2021's trading, but concerns related to the pandemic and inflation are also creating volatility. 

Some industry-leading companies with huge growth potential have seen their valuations dinged amid market uncertainty, and investors who seize on the right buying opportunities could enjoy stellar returns. With that in mind, read on for a look at three top stocks that are worth adding to your portfolio before July falls off the calendar. 

Money sticking out of the sand.

Image source: Getty Images.

1. Airbnb

Airbnb (NASDAQ:ABNB) has already disrupted the travel space, and its name is virtually synonymous with the short-term vacation rental category. Surging cases of the COVID-19 delta variant might be complicating the company's near-term outlook, but the long-term opportunity here remains very promising. 

Despite pandemic-related challenges, Airbnb managed to grow revenue 5% year over year in the first quarter, and the business still has a huge runway for expansion. The company is on track to benefit from a powerful network effect as it attracts more hosts and guests to its platform.

More hosts joining means that guests will have a greater variety of potential accommodations to choose from. And more guests joining will create added incentive for new hosts to join the platform and for existing hosts to expand their offerings. It's a beautiful cycle -- and one that will likely continue to bolster the company's already very strong position in the travel and hospitality industry. 

Airbnb is also making a big push in the travel experiences category, pairing its property rental services with options to buy tickets for local events and attractions. This should help strengthen the platform's overall value proposition by providing discounts for guests, and it could boost margins through sponsored promotions and by increasing the average spending per booking. 

With a market capitalization of roughly $84 billion, Airbnb already has a sizable valuation, and that might raise questions about how much room for growth is really left. As impressive as the company's rise has been, its growth story is likely just getting started. For investors willing to embrace some volatility and buckle in for the long term, Airbnb offers a very attractive risk-reward dynamic at current prices. 

2. Electronic Arts

Top video games command levels of engagement and monetization that far surpass releases in pretty much every other entertainment medium, and leading companies in the space stand a good chance of delivering strong returns for shareholders. Within that mold, Electronic Arts (NASDAQ:EA) stands out as a worthwhile play that looks poised to deliver big wins. 

The company is best known for sports properties including FIFA and Madden NFL and action series such as Apex Legends and Battlefield, but it has a deep bench of franchises and development studios that should help it tap into the growth of the global games industry. EA is also looking a lot stronger following its acquisition of Glu Mobile.

As a Glu shareholder prior to the acquisition's completion in June, I thought that the $2.4 billion buyout underestimated the mobile games specialist's growth potential, and I would have preferred that the smaller publisher remained independent. It looks like EA got a good deal on the acquisition, and I think that Glu can play a big role in powering the company's next growth phases. 

EA stock price is down roughly 4% over the last three years, and shares look attractively valued in the context of the company's strong franchise catalog, development resources, and growth opportunities in mobile. With the company's stock trading at roughly 22 times this year's expected earnings, long-term investors who build positions at today's prices could enjoy a big upside. 

3. The Trade Desk 

The Trade Desk's (NASDAQ:TTD) digital advertising platform uses data analytics to help ad buyers run more effective campaigns. The digital ad market has seen huge growth over the last two decades, but it's also becoming increasingly competitive, and that's creating demand for services that can help advertisers thrive and tailor the delivery of materials to the viewers most likely to be responsive. 

Despite posting growth last year, the overall digital advertising market was still pressured by the pandemic. Companies cut down on growth initiatives, consumer spending tightened, and advertising rates generally came under pricing pressure due to weak demand. The Trade Desk benefited from a boom in streaming video engagement, but it should also benefit from economic recovery and more robust spending in other digital advertising channels. 

Growth-focused investors have an opportunity to take advantage of a pullback for the stock this year. The Trade Desk's share price is down roughly 25% from its 52-week high following volatility for growth-dependent tech stocks. The stock was also affected by shifts in user data tracking by browser operators including Alphabet and Apple, which could hurt growth potential for digital advertising companies.

However, Alphabet has delayed the rollout for its new third-party data tracking policy until 2023, and The Trade Desk already has solutions that should mitigate the impact of the change. It's also worth noting that the change only affects browser-based tracking and not the connected-TV services at the heart of the company's business. 

With consumer spending picking back up and growth for programmatic advertising in streaming video and other markets still in its early innings, The Trade Desk is primed to serve up more wins for shareholders. 

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.