The main purpose of this paper is the investigation of Persian modal auxiliary verbs in the framework of force-dynamic model of Talmy and idealized cognitive model of Langacker. Force-dynamic model which stands, originally, for the analysis of action and reaction of physical objects in the real world, has been used by Talmy for characterizing the deontic notion of modal auxiliaries and then, extended by Sweetser for conceptualizing the epistemic reading of modals. The investigation of deontic and epistemic notions of modal auxiliaries on the basis of this model, revealed that the actualization of the event is not guaranteed but it is actualized in the nonfactual world. The second model, i.e., the metaphoric idealized cognitive model, known as epistemic model, is proposed by Langacker under the influence of Lakoff's theory of idealized cognitive models. The investigation of modal auxiliaries in the framework of this model showed that modal auxiliaries are not under epistemic control and fall in the realm of irreality and with respect to the rate of momentum construed to the specified event, the modals locate in a near of far distance from immediate reality. By comparing the results of the two models, it is revealed that not being under epistemic control equals not being guaranteed and on the other hand, actualizing the situation in nonfactual world means falling in the scope of irreality; so, the two models cooperate in conceptualizing the Persian modal auxiliary verbs.