The following represents the sort of “metaphysic” I follow, in regard to a God-world relation. It flows from Barth’s style of actualism, and as you will see, it coheres with his stance contra natural theology. If there is anything, beyond election (and these things are related), that has attracted me most to Barth’s theology, it is this actualist alternative to the theological ontology that funds the various classical theisms. In order to understand what I am referring to, if you don’t, we will read along with Darren Sumner, as he describes Barth’s actualism. The following comes from Darren’s published PhD dissertation entitled Karl Barth and the Incarnation: Christology and the Humility of God.
Barth’s methodology thus follows from his doctrine of revelation: there is no creaturely basis for theological speech, which is only speech after God, who summons creatures to an act of repetition in witnessing to His Word. This task thus begins not with philosophical presuppositions, nor with the creature’s speculation or erection of descriptive categories by which revelation might be understood, but with the event of God’s activity in history—an activity to which Scripture is witness and that has its telos the very presence of God in Jesus Christ. While this may seem self-evident to Christian theologians, Barth’s theology demonstrates the real and radical consequences of strictly adhering to such a method—and thus exposes the tradition’s occasional failures to engage in its task from this starting point and no other.
But because revelation is the utterance of a Word that is God Himself, this epistemology has further ontological implications. Barth’s actualistic ontology describes not only revelation but also the being of God in His activity, over against that which is regarded as a speculative essentialism—that is, a God who exists logically prior to and apart from His works. God is therefore not one who acts, but is His activity. God exists in motion, a motion that springs from the abundance of God’s love and is directed toward creatures. God’s being is pure act—a classically Augustinian way of speaking of divine simplicity and aseity, but which Barth insists is to be anchored in that one event in which God has actually made Himself known to creatures. “God is” means “God loves,” and all further insights about who God is must revolve around this mystery of His loving. Such an ontology suggests that God is the Lord even of His own existence, because God sovereignly wills the activity by which He determines His being. (Thus Barth located election within his doctrine of God, not in creation or reconciliation.) God’s self-determination to be God for creatures—the God of the covenant (Lev. 26.12–13)—has the incarnation of the Son as its fulfillment.
Actualism therefore identifies both Barth’s methodology and divine ontology because revelation and reconciliation are interdependent. Revelation is reconciliation, and vice versa. Revelation is, further, God’s own self-disclosure, which is to say that in Christ God has communicated His own divine life and not merely information about Himself. As Wolfhart Pannenberg put the matter: “The Revealer and what is revealed are identical. God is as much the subject, the author of his self-revelation, as he is its content.” Therefore the Christ event, the divine-human life of Jesus, “belongs to the essence of God himself.” The theological speech of men and women, therefore, must remain continuously attentive to the history of Jesus Christ as the fulfillment of the covenant. Each aspect—God’s self-giving to creatures in revelation and reconciliation, and God’s own, inner life—is in the dynamic movement of act and giving, never in fixed form.
This articulation from Darren helps to reinforce what I have been presenting here at the blog for many years. This is why it is rather hard to bring Barth’s theology, and the classical theistic theology being retrieved by so many up-and-coming theologians in the evangelical churches into relief. There is a distinct theological ontology—an ontology that is explicitly shaped by dynamic relational characteristics versus those offered up by the ‘substance’ metaphysics imbibed by reference to classical Greek philosophers—that left unrecognized will stymie any sort of fruitful rapprochement, or at least some semblance of dialogue between the theologians.
More applicably: For me personally, Barth’s actualism works much better with the God we come up against in encounter with Him in Holy Scripture. The God we encounter, in Christ, is indeed, the only face of God that the Christian actually knows. We don’t know a prior God to the God that we have met in Jesus Christ. The Christian’s concept of God, particularly the Protestant’s, is grounded in the reality we meet narrated to us through the pages of Scripture. This is why we can say that Barth’s theology is genuinely Protestant in orientation; while he is working constructively with the tradition, and the so called Chalceonian settlement, his primary norm is what is taught in Scripture. But in order to genuinely value this, the Protestant must indeed be committed to semper reformanda in the sense that the organicism of Scripture’s reality (res) gets to shape the categories and emphases through which God is known. All too often, precisely because many Protestants want to cull the ‘catholic’ heritage, what is abandoned, in function, is this sort of principial commitment to Scripture as the norming norm. These sorts of Protestants end up truncating Scripture by reference to the ecumenical creeds, thus disallowing Scripture (signum) and its reality (res) to provide primary shape for how the Christian thinks God.
Much more could be said, but actualism, and Barth’s style of it as applied to a doctrine of God in Christ, undercuts the sort of theological essentialism that defines the various classical theistic traditions and retrievals currently underway. It undercuts precisely at the point that he is attempting to understand who God is by encountering God afresh and anew in Holy Scripture, and allowing that to be the canon by which all other permutations—no matter what their accrued pedigree—are measured by. Barth’s theological approach is indeed Protestant in the best spirit of that Word; i.e. in the sense that his theology is first and foremost committed to the Protestant Scripture principal. When we look around at the landscape of Reformed theologies in the evangelical theologians today, I would argue that the same can’t be said, ultimately.
 Darren O. Sumner, Karl Barth and the Incarnation: Christology and the Humility of God (New York: Bloomsbury T&T Clark, 2014), Loc. 326, 334, 342, 350.