The Commentary on the Song of Songs is by far the most important and most deeply theological work of A. Gálvez, and it is divided in two volumes. In the first, composed of an introduction and three different sections (one for each of the first three verses of the Song of Songs), the author lays out that which is most specific to his thinking, namely, his theological/metaphysical theory concerning Divine Love as manifested in the Incarnation. Why did God become Man? Was our Redemption the only reason that God should take upon Himself a human nature that differed in no way from ours except for sin? If there is another reason, to what extent is it related to Man´s ultimate purpose or to the description of his very essence? God became man in Jesus Christ so that He could express his Love in a human way, and so that man could also love God back in a human way, with all his heart, with all his soul, and with all his being. Christ's Humanity expresses His Divinity: “Phillip, who has seen Me, has seen the Father”. The face of Christ, his human gaze, is the expression of Divine Love manifested to man more humano. This is, for A. Gálvez, the great Revelation of the New Testament. According to the author, “to love God with a true and perfect love...the human heart needs God to make Himself known to it in through a human nature.” 
 
By the light of the first verses of the Song of Songs, the author presents the main elements of his theory: Love is a relationship that is eminently personal, and therefore only between persons can there be a bond of love. From this, he derives a proposal for a metaphysical description of the status of a person, an explanation of that which makes a person incommunicable. A person is a being that can give everything up except the very ability to give. It is evident that this theory is based on the thought of St. Thomas of Aquinas and on the use of analogy. With the help of this concept, the author moves between the divine level of Love in the bosom of the Holy Trinity to the divine-human love between God and man through Jesus Christ, without forgetting to offer (on a few specific occasions)  an explanation of love on a purely human level.