Shoulder presses work the muscles in your shoulders and upper chest, including the deltoids, trapezius, and triceps. The anterior deltoid is the primary muscle worked during the shoulder press, but the lateral deltoid, triceps, upper chest, and traps are also secondary muscles that are activated during the exercise. Additionally, the stabilizer muscles in your shoulders, elbows, and wrists are engaged during the exercise, which can help improve your stability and balance. Performing shoulder presses with proper form can help improve your upper body strength, posture, and decrease the risk of osteoporosis.