To style a men's lightweight polo shirt in summer, pair it with breathable chinos or tailored shorts for a cool, casual look. Opt for light colours like white, pastel shades, or soft blues to stay fresh. Match with comfortable loafers, espadrilles, or sleek trainers. Keep accessories minimal; a simple watch or pair of sunglasses will enhance the summery vibe. Tuck in for a slightly dressier feel or leave untucked for a relaxed appearance. Ensure the fit is easy but well-proportioned to maintain comfort and style in the warmer weather.