Is This a Stock Market Melt-Up? Here Are Ways to Tell

The stock market is on a tear again, with high-flying technology stocks propelling the S&P 500 Index toward fresh records and luring swaths of momentum-chasing investors. Speculation that the worst of war in Iran is over has traders piling into artificial intelligence darlings such as Broadcom Inc. and Intel Inc. — and sent semiconductor stocks higher in 21 of the last 23 trading sessions.

But the sudden surge has prompted some on Wall Street to suggest that the market is experiencing a “melt-up.” That’s market lingo for situations when prices rise sharply as buyers pile in to avoid missing out on a rally. Since the rapid run-up tends to be driven by momentum rather than company fundamentals, the gains also can evaporate quickly.