Until reading Dr. Peter Kreeft's Socratic Logic chapter on definitions, I had no idea that "God is Love" (1 John 4:16) is a metaphor. Quote from Section 4 (The limits of definition) page 129:
As far as God is concerned, we can only say (a) what God is not or (b) what God is like. But this is not to define God, for each of these two choices violates a rule of definition. (a) If we use literal, univocal language, we can only say what God is not, not what God is. (E.g. God is not a man, God is not a body, God is not in time.) But God is not a negative thing, like nonbeing or death or evil. So a negative definition of God would violate one of the rules of definition (rule #5). (b) If we use analogical or metaphorical language, we can speak positively, but only to say what God is like, not what God is, literally. (E.g. we can say that God is a Father, God is Love, God is a King. But God is not a human biological father or the changeable human passion of love, or an earthly political ruler.) And of course non-literal language violates another rule of definition (rule #3).
I don't really know why this blew my mind, but I had always taken those words and thought of them as literal (I still think they can and should be taken literally as well). And I've read a number of answers on this site recently that also take only a literal interpretation.
But according to the Catholic Catechism, there are four senses of scripture, so what have saints, popes, councils and other good exegetes, said about what does "God is love" means from a Metaphorical, Literal, Anagogical and Moral sense? I'd prefer answers that hit on all four senses bullet point style unless there's a very good reason for excluding one.