The month of May has finally arrived! As the air grows warm and flowers start to bloom in earnest, it might be tempting to sit back, relax, and plan your impending summer activities -- and by all means, do so.

But if you have any money not pegged for vacations, summer camp, or neighborhood barbecues, you shouldn't let it relax too. Instead, consider putting it to work in the stock market.

To aid you in that pursuit, we asked five top Motley Fool investors to each pick a stock they think investors would do well to buy this month. Their choices: Amazon (NASDAQ:AMZN), Alphabet (NASDAQ:GOOG)(NASDAQ:GOOGL), Celgene (NASDAQ:CELG), Walmart (NYSE:WMT), and Skechers (NYSE:SKX)

Stacks of successively taller coins with small plants growing out of the tops

IMAGE SOURCE: GETTY IMAGES

Nothing not to love

Steve Symington (Amazon.com): Shares of Amazon fell hard in late March and early April after President Trump repeatedly -- and incorrectly -- criticized the company over items including its tax status and relationship with the U.S. Postal Service.

But if the first-quarter report it delivered last week is any indication, that pullback was a blessing in disguise for investors who wanted to add to their positions or open new ones. As I read through that report, I realized there was nothing not to love about its results. From its thriving e-commerce business to its ridiculously profitable Amazon Web Services (AWS) segment, and with its acquisitions of Whole Foods Market and video-doorbell leader Ring, Amazon is truly firing on all cylinders.

More specifically, Amazon's revenue last quarter skyrocketed 43% year over year (or 39% in a constant-currency basis) to a staggering $51 billion, arriving $200 million above the high end of Amazon's own guidance. Looking toward the bottom line, operating income jumped 92% from last year's Q1 to $1.9 billion, crushing the $1 billion high end of Amazon's outlook. 

Perhaps its outperformance shouldn't have been a surprise. A week earlier, founder and CEO Jeff Bezos confirmed that the Amazon Prime service recently exceeded 100 million members. Those members not only enjoy the fast free shipping on millions of items for which Prime is best known, but also have access to Prime Music, Prime Instant Video, discounts at Whole Foods, and dozens of other little-known benefits. In fact, Amazon even used those benefits a few days ago to justify increasing the price of Prime by $20, to $119.99 per year, marking its first price hike in four years. 

Even putting aside the cash flow that hike will provide Amazon in the coming quarters, Amazon would still look virtually unstoppable. And I think there's plenty of room to rise for investors who buy this month.

You won't go wrong with Alphabet

Anders Bylund (Alphabet): The company formerly known as Google is still the premier internet business on the planet. The name change simply signaled its willingness to evolve with the times and stay relevant as the internet we know and love transforms into something else.

If there's one quality I require above all others before making an investment, it's flexibility. A company that's absolutely set in its ways is more likely to attempt to stop the world from changing than to adapt, and that's a recipe for disaster. Not even a giant of Alphabet's heft can stop time. So I'm thrilled to see it planning for a vastly different future.

The Google unit and its related businesses accounted for 98.9% of Alphabet's total sales in 2017. No other operation was significant enough to merit a financial report of its own, so they're all just lumped into the "other bets" category for now. But the times, they are a-changin'. The non-Google segments produced just 0.5% of Alphabet's revenues as recently as 2015, and "other bets" sales have nearly tripled since then.

In the long run, Google-centric operations such as online search and advertising services should give way to more hands-on business ideas. Early contenders for the Next Big Thing title include Waymo's self-driving cars and the Calico-branded medical research hub. In due time, those might be the first things that come to mind when we think about Alphabet, as the old Google name fades into the background.

That's the bird's-eye, long-term reason why I recommend Alphabet shares at almost any price. But it's also a fairly volatile stock for a company of this size -- Alphabet is closing in on a trillion-dollar market cap -- so why not take advantage of a temporary discount? Both Class A and Class C shares are trading roughly 14% below their 52-week highs now, after Wall Street shrugged off the solid momentum on display in the Q1 report to focus on short-term flaws.

Investors today are getting a clear-eyed business with fantastic long-term prospects at a discounted share price. Sounds like a great buy-in opportunity to me.

A classic overreaction to bad news that isn't that bad

Sean Williams (Celgene): Though I've sounded the horn on biotech blue chip Celgene before, I'm going to do it once again by proclaiming it my top stock to buy in May.

Shares of Celgene were pummeled relative to its peers during the past 12 months. The company revised its 2020 sales and profit targets in October, and announced a delay in getting potential blockbuster drug ozanimod in front of the Food and Drug Administration (FDA) for approval as a treatment for multiple sclerosis.

With regard to its weaker 2020 outlook, a slower uptick in Otezla's sales in recent quarters, along with increasing competition for cancer drug Abraxane as a result of next-generation immunotherapies, led Celgene to be more cautious with its sales and profit guidance.  As for ozanimod, the FDA requires additional studies to be run before it'll consider the drug for approval. Analysts at Morgan Stanley (NYSE: MS) have suggested that the approval process could be delayed by up to three years while these additional studies are completed. 

This might all sound terrible, but it's really not. Wall Street is once again looking past what really matters here: multiple myeloma drug Revlimid, and its patent expiration date.

Last year, Revlimid accounted for $8.19 billion (63%) of the company's $12.97 billion in net product sales.  The concern is obviously that once Revlimid is exposed to generic competition, Celgene will crumble. But this thesis overlooks two key points. First, Revlimid demand and use is on the rise. Better diagnostic equipment and a growing global population is leading to earlier diagnoses and a growing number of aggregate multiple myeloma diagnoses. As a result, the average duration of use for Revlimid has increased, putting the ball in Celgene's court when it comes to pricing power.

Secondly, Celgene's management team has covered its bases. In December 2015, the company settled with a handful of potential generic entrants, protecting its prize drug from competition until March 2022. Even then, only a relatively small amount of generic Revlimid will make it to market. The pharmaceutical company's core product is essentially protected all the way through January 2026 from a flood of generic entrants.  

Therefore, even if ozanimod is delayed by two to three years, it's not as big a deal as you might think given that Revlimid should remain a cash cow for Celgene for almost eight additional years. Sure, it's a bit disappointing that the FDA is requiring additional studies, but it's not a game-changer for the company's long-term growth potential. Plus, with dozens of partnered or licensed experimental products in its back pocket, it certainly isn't hurting for opportunities. Given its double-digit percentage sales growth rate and forward P/E of less than 9, growth- and value-seeking investors should give Celgene a closer look.

Not your father's Walmart

Jeremy Bowman (Walmart): Few turnaround stories have been more impressive than Walmart's in recent years. CEO Doug McMillon took a retailer that was floundering amid the changing industry landscape, and with smart decisions like raising wages, investing in the current store base, and acquiring Jet.com, returned it to stable growth. Last year, the stock jumped 43% as McMillon's turnaround plan began to deliver results.

However, shares sold off following a disappointing fourth-quarter earnings report in February. Investors were discouraged that Walmart's U.S. e-commerce growth slowed to 23% after jumping 50% in the third quarter. Management blamed the slowdown on some temporary operational issues as well as the lapping of the Jet.com acquisition the year before, and maintained its forecast of 40% U.S. e-commerce growth this year.

With Walmart's first-quarter earnings report coming up later this month and the stock still down 20% from its 2018 high, this looks like a great opportunity to buy. If the company beats earnings estimates, the stock is likely to surge as the concerns that arose following the fourth-quarter report dissipate, and even if it doesn't, there are still a number of positive catalysts that could propel the stock upward.

Walmart just completed the merger of its U.K.-based subsidiary Asda with Sainsbury, a deal that will yield the company $4.1 billion in cash and 42% of the new combined company. That likely sets up Walmart to take a majority stake in the leading Indian e-commerce player, Flipkart, for about $10 billion, as the company wisely pivots toward growth markets. A rumored plan to acquire health insurer Humana also adds intrigue.

With a rapidly improving retail business and a blockbuster acquisition or two on the horizon, Walmart is no longer the stodgy big-box chain many think of it as. Take advantage of the discount on the stock while you can.

Another major overreaction

Tim Green (Skechers): Shares of footwear company Skechers took quite a dive in April. About one-third of Skechers' market value has vanished since the company reported its first-quarter results on April 19, despite solid numbers. What happened? Second-quarter guidance wasn't so hot.

Skechers said it expects growth to slow down, and called for revenue to expand by a little over 10% year over year at the midpoint of its guidance range. That's not nearly as impressive as the 16.8% growth the company managed during Q1. The bottom line is the bigger concern. Management expects earnings per share to land in a range from flat to up 13.2% in Q2, compared to a 25% gain in Q1.

Skechers blamed the weaker guidance on some shipments being pushed into the second half of the year. That may foreshadow softening demand for the company's products, or it may simply be a temporary issue. Either way, the stock price has dropped so far that the company doesn't need to hit home runs to be a solid investment from here.

If you back out the $615 million of net cash on Skechers' balance sheet, the stock trades for about 14 times 2017 earnings and less than 11 times the average analyst estimate for 2018 earnings. This is a company that's still growing at a double-digit percentage pace, albeit with earnings growth set to slow. Given that the S&P 500 trades for around 24 times trailing-12-month earnings, Skechers doesn't deserve such a beaten-down valuation.

Skechers has a rock-solid balance sheet and plenty of growth opportunities in its international business. Take advantage of the market's overreaction and pick up some shares of this company in May.

The bottom line

We obviously can't guarantee that any of these five promising stocks will beat the broader market from here. But outperforming is certainly our goal. And between Amazon's incredible business momentum, Alphabet's healthy core Google operations and flexible "other bets" units, Walmart's improving retail business and acquisition potential, and the negative overreactions to both Celgene's and Skechers' recent earnings reports, we like their chances of doing that. We think investors would be smart to buy accordingly.

John Mackey, CEO of Whole Foods Market, an Amazon subsidiary, is a member of The Motley Fool's board of directors. Suzanne Frey, an executive at Alphabet, is a member of The Motley Fool's board of directors. Anders Bylund owns shares of Alphabet (A shares) and Amazon. Jeremy Bowman has no position in any of the stocks mentioned. Sean Williams has no position in any of the stocks mentioned. Steve Symington has no position in any of the stocks mentioned. Timothy Green owns shares of Skechers. The Motley Fool owns shares of and recommends Alphabet (A shares), Alphabet (C shares), Amazon, Celgene, and Skechers. The Motley Fool has a disclosure policy.