The Light wire is an orthodontic appliance primarily used for fixed mechanical tooth movement, not for modifying muscle function or oral habits. In contrast, the Frankel appliance, Bionator, and Activator are all myofunctional appliances designed to correct dysfunctional muscle patterns and guide jaw growth by harnessing the action of orofacial muscles. Therefore, the Light wire does not fall under the category of myofunctional appliances because it lacks a functional component acting on muscle function or posture.

Reference: Graber's Orthodontics, 6th Edition.