The deltoids are the muscles that allow humans to raise their arms laterally. In addition to the deltoids, there are several other muscles groups that assist in lateral motion.
In the deltoids, the front and side sections of the muscle are the parts that are most responsible for moving the arm forward and up. In conjunction with the deltoids are rotator cuff muscles and the scapular muscles. Rotator cuff muscles are essential for stabilizing the shoulder joint and making the internal motion of the humerus bone smooth and fluid. Two scapular muscles, the trapezius and the serratus anterior, are crucial in shoulder blade movement, which is part of what makes the lateral motion of the arm possible.