By Nate Wolf and Mackenzie Tatananni
The stock market just keeps on keeping on. The S&P 500 rose 5.1% in May, building on a 10% gain in April. If Friday's gains hold, the index will have climbed nine consecutive weeks -- its longest streak since 2023.
Tech stocks led the way in May, as they have throughout this extended rally. Here are the best and worst S&P 500 stocks this month as of Friday's opening bell.
The Leaders
Dell Technologies stock surged 104% in May. The PC and server maker finished the month strong, breezing past analysts' expectations for earnings and revenue in its fiscal first quarter. A Barron's stock pick last fall, Dell is seeing intense demand for servers and networking equipment at artificial-intelligence data centers. The company forecast AI server revenue of $60 billion in fiscal 2027, up from $24.7 billion in 2026.
Micron Technology continued its hot run in May, rising 84%. The memory chip maker is benefiting from AI demand and a supply shortage that has boosted prices. Micron shares have climbed more than 900% in the last 12 months, and the company hit a $1 trillion market capitalization for the first time earlier this week.
What software slump? Observability platform Datadog has managed to buck the downtrend in software stocks, establishing itself as a necessary tool for the AI boom. The stock rose 75% this month, with the bulk of those gains coming after Datadog posted better-than-expected earnings and lifted its full-year guidance on May 6.
Super Micro Computer spiked 69% in May -- not quite as good as its rival, Dell, but not too shabby. The server maker needed a boost after the federal government charged a Super Micro co-founder and two other individuals -- though not the company itself -- in an alleged plan to smuggle U.S.-assembled servers to China. While quarterly earnings were mixed in early May, overall momentum in the server trade was enough to bring the stock back to life.
Data storage company NetApp rounded out the top five, jumping 65% and breaking past its old dot-com era highs. The stock spiked 28% on Friday after beating earnings and revenue expectations for its fiscal fourth quarter.
The Laggards
Zoetis was the month's biggest decliner, falling 32%. That steep drop stems from a guidance cut at the start of May, when the animal health company lowered its full-year earnings outlook to a range of $6.85 to $7 a share, down from $7 to $7.10 previously. CEO Kristin Peck said at the time that a tough consumer spending environment was forcing pet owners to become more price-sensitive, leading to fewer vet visits and lower demand for premium products.
AutoZone cratered 20% in May after fiscal third-quarter earnings revealed sluggish growth in AutoZone's two international markets. Comparable sales rose just 1.6% on a constant-currency basis in Mexico and Brazil, marking a slowdown from the 2.5% growth recorded in the prior quarter.
Shares of Trimble slumped 19% this month. The stock fell for seven days straight after the technology provider, whose offerings are tailored to the construction and farming industries, issued a soft second-quarter outlook, triggering a wave of downward price target revisions at several firms. Adding to the pressure, investors have also grown increasingly concerned over Trimble's high valuation
Intuit, the maker of software programs like Turbotax and QuickBooks, saw its stock decline more than 18%. While recent quarterly earnings beat expectations, Intuit announced a round of layoffs. The company said it plans to reduce its full-time workforce by 17%, though CEO Sasan Goodarzi asserted that AI "had no bearing" on the decision in an interview with Barron's .
Insulet sank 17%, extending a losing streak from April, when it appeared in Barron's previous list of worst monthly performers. Despite strong quarterly results, shares sold off at the start of May after the medical device maker guided to weaker-than-expected second-quarter U.S. sales of its Omnipod insulin pump. On May 27, the company flagged a manufacturing issue affecting roughly 7 million insulin pod medical devices.
Write to Nate Wolf at nate.wolf@barrons.com and Mackenzie Tatananni at mackenzie.tatananni@barrons.com
This content was created by Barron's, which is operated by Dow Jones & Co. Barron's is published independently from Dow Jones Newswires and The Wall Street Journal.
(END) Dow Jones Newswires
May 29, 2026 15:47 ET (19:47 GMT)
Copyright (c) 2026 Dow Jones & Company, Inc.
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