This work is an interpretation of the main aspects of Plato`s philosophy as Metaphysic`s beginning, enlightened by Martin Heidegger`s thinking. With the regard founded in the contemporary world and the comprehension of the technology`s essence that first came to light with Martin Heidegger, it aims to enlighten the forgotten ground of metaphysic`s onto-theo-logical essence that begins with Plato, i.e., the retrial of the aletheia as original happening favoring a way of unconcealment of being as substance, with the correlate postulation of a supreme being that founds the adequacy between being an thinking. It shows how this original accord starts metaphysic`s decline in the modernity, with Cartesian thinking, giving another way of unconcealment: o Gestell, the technology`s essence. In this perspective the study analyses the next Plato`s dialogues: Meno, Republic, Symposium, Sophist and Timaeus. The work presents too an analysis of the consequences of the decline of substance notion in the modernity, in Descartes and Kant`s philosophies, as well as a critical exposition of those contemporary conceptions that understand technology as essentially having an instrumental character.