What is the name of the large triangular muscle that covers the shoulders and helps lift and turn the arms?

The large triangular muscle that covers the shoulders and plays a key role in lifting and rotating the arms is known as the deltoid muscle. This muscle is shaped like an upside-down triangle and is situated on the uppermost part of the arm and the shoulder. It has three distinct portions—the anterior, lateral, and posterior fibers—that work together to allow a range of arm movements, including abduction, flexion, and extension.

The deltoids are essential for various activities such as lifting, throwing, and other overhead movements. Their structure enables efficient movement and stabilization of the shoulder joint, making them a critical muscle group for both athletic performance and daily activities. Understanding the function and location of the deltoids helps in various fields, including physical therapy, personal training, and sports medicine, making them significant to esthetics practitioners who may work with clients focusing on fitness and body aesthetics.