The neck muscles can be separated into anterior (front) neck muscles and posterior (back) neck muscles. However, it is the back of the neck that is the most muscular.
Five major muscles in the back of the neck are the trapezius, levator scapula, splenius, suboccipitals, and posterior cervical muscles. The trapezius muscles connect between the neck, shoulders and back. They are used to lift the shoulder up towards the ears. The levator scapula connects between the neck and shoulder. It is used to lift and shoulders and turn the head. The splenius muscles connect the back of the head and neck with the vertebrae of the upper back. The splenius muscles are used to rotate the head and tilt it backward. The suboccipitals connect the skull with the top two vertabrae in the neck. They are used for the yes and no motions of your head, and side bending of the head. Lastly, the posterior cervical muscles along the back of the neck extend your head backwards.
In the front of the neck, the sternocleidomastoid muscles help with flexing and rotation of the neck. They connect from the upper side of the neck to the lower front of the neck. The infrahyoid or strap muscles connect the respiratory skeleton and sternum. There are also muscles connecting the hyoid to the tongue, mandible, and styloid.