From Tim Keller in “The Reason For God: Belief in the Age of Skepticism“:
If there is no God, then everything in and about us is the product of blind impersonal forces. The experience of love may feel significant, but evolutionary naturalists tell us that it is merely a biochemical state in the brain.
But what if there is a God? Does love fare any better? It depends on who you think God is. If God is unipersonal, then until God created other beings there was no love, since love is something that one person has for another. This means that a unipersonal God was power, sovereignty, and greatness all from eternity, but not love. Love then is not the essence of God, nor is it at the heart of the universe. Power is primary.
However, if God is triune [Father, Son, Holy Spirit], then loving relationships in community are the “great fountain … at the center of reality.” When people say “God is love,” I think they mean that love is extremely important, or that God really wants us to love. But in the Christian conception, God really has love as his essence. If he was just one person he couldn’t have been loving for all eternity.