is the deltoid a superficial muscle
1 It also draws the shoulder downward and backward and keeps the inferior angle of the scapula against the chest wall. 2  Side (lateral) muscles of the shoulder: 3  The large deltoid muscle provides the characteristic contour of the shoulder and is the largest, strongest muscle of the shoulder. It also draws the shoulder downward and backward and keeps the inferior angle of the scapula against the chest wall. 2  Side (lateral) muscles of the shoulder: 3  The large deltoid muscle provides the characteristic contour of the shoulder and is the largest, strongest muscle of the shoulder.