This post is a possibly obscure but hopefully not unduly speculative reflection on the relationship between the immanent and economic Trinity. If that doesn't interest you, you probably shouldn't read it...
When we affirm, with the Scripture, that God is love, I take it we are in fact saying two things: one thing about God - Father, Son, Holy Spirit - in terms of God's own internal life and existence; and one thing about God - Father, Son, Holy Spirit - in terms of God's relationship to that which is outside himself, namely the creation in all its varied orders.
In the first sense, 'God is love' affirms the eternal relation of love between the 'persons' of the Godhead within the unity of the One God. The Father loves the Son; the Son loves the Father; the Father and the Son love the Spirit - and all these relations are reciprocal. (Though not, I take it, symmetrical - the Father loves the Son as Son, the Son loves the Father as Father etc. This is important, because the Son's love for the Father includes the desire to obey, which the Father's love for the Son does not include). We might call this God's love by nature. Because God is three-in-one-in-love, there never was a time when there was not love at the heart of who God is. This is a powerful apologetic against Islam, incidentally - can a monad, such as the Islamic conception of God, in fact be described as loving? Certainly not by nature, unless we are also willing to ascribe a loneliness and incompleteness to the monad, which is filled only by the creation. However, when we say that the Trinity is love by nature, we imply no lack, because of the plurality of persons and therefore the reality of eternal loving relations. Note that this love is 'natural' in at least two senses. It is natural that this love be given because it belongs to the character of each person to love; and it is natural that this love be given because each person is worthy of love.
In the second sense, 'God is love' means that God loves his creation. At the most basic level, God creates, and no rationale can be given for this except his love. He sustains and provides for all he has made, which is to be attributed to his love. And of course, supremely God the Son enters his creation in the person of Jesus Christ, redeeming it by his wrath-bearing death and life-giving resurrection. In fact, tracing the relations of the Father, the Son and the Holy Spirit with creation through the Scriptures reveals that each person is intimately involved in the existence, sustenance and redemption of the created order, and all because of love. This love, however, is not natural in the sense that the intraTrinitarian love is. If it were, God would have had to create, and then would have to redeem his fallen creation. But the Scriptures marvel at his grace in doing both of these things in a way which certainly rules out any notion of necessity. God creates freely, sustains freely, redeems freely. He loves his creation because he wills to do so. It exists because he wills to love it, and is redeemed because he wills to continue to love it.
God's relation to his creation is thus a willed extension of what is natural in himself. But is it right that God will this extension? Is it not idolatry for God to love something other than himself? How can the self-sufficient, glorious God love creation?
The key is the incarnation. The Father loves the Son, by nature; but he wills to love the Son as incarnate. When the Scripture describes Jesus Christ (the man) as the logic that underlies creation (consider John 1 as a whole and Colossians 1:15ff for starters), the authors are asserting that everything that is ontologically 'outside of' God exists for the purpose of Christ's kingdom. It exists that the man Jesus Christ might rule. It exists that the man Jesus Christ might be. And the man Jesus Christ is loved because the Father wills to love his Son in flesh, just as he naturally loves him in the eternal unity of the Godhead. Space and time exist for the incarnation of the Son of God. History exists for the rule of the Lord Jesus Christ. God's willed love for his creation is his love for his Son as incarnate, and therefore is not idolatrous but is a true reflection ad extra of the internal love of the Godhead.
In short: Glory to the Father, and to the Son, and to the Holy Spirit, as it was in (and before!) the beginning, is now and ever shall be. Amen!