The S&P 500 (SPX) closed lower on Monday as tensions remain elevated between the U.S. and Iran.

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Let's break down the sectors behind the performance.

Today's Top-Performing Sector

Communication services was the top-performing sector, with Alphabet (GOOGL) leading the way higher. Earlier today, The Information reported that the tech giant is developing a next-generation AI server chip powered by Gemini, with a planned 2028 launch. Furthermore, AT&T (T) and T-Mobile (TMUS) were both top performers ahead of their earnings on July 22 and July 23, respectively.

Several communication services stocks led the sector's gains, including:

• Alphabet (GOOGL)
• T-Mobile (TMUS)
• Take-Two Interactive (TTWO)
• AT&T (T)
• Omnicom (OMC)

Today's Worst-Performing Sector

Meanwhile, the healthcare sector faced the largest drawdown. Moderna (MRNA) continued to sell off, bringing its five-day loss to 10%. In addition, the sector as a whole faced pressure from a rising 10-year Treasury yield. With higher yields, earnings expected further in the future are discounted more heavily, weighing on valuations. Healthcare stocks are especially sensitive to higher yields because a larger share of their value is generally tied to long-term earnings expectations.

Notable healthcare stocks trading lower include:

• Moderna (MRNA)
• Revvity (RVTY)
• Mettler-Toledo International (MTD)
• Waters Corp (WAT)
• Biogen (BIIB)