"God is love" is a direct quote from two different biblical passages: 1 John 4: 8 and 1 John 4:16. However, there are many other Scriptures that express this truth-which describes the essence of God's nature-in a different way.
Some examples are John 3:16 (another much quoted verse): "For God so loved the world ..."; John 16:27: "For the Father himself loves you" and 1 John 3: 1, where the apostle John also tells us about God's love saying: "Look at what love the Father has given us."
And these are only a small sample of many Scriptures that reiterate this fundamental characteristic of the nature of God. God is love, and expresses his love for us in different ways.
What does "God is love" mean? Experts have tried to explain it by describing God as "pure goodness" (Barnes Biblical Commentary). Or, as we read in the Jamieson-Fausset-Brown Bible Commentary: "God is fundamental and essentially LOVE: not simply loving."
However, no expert tells us about God's purpose - what his nature, love, has motivated him to do. And, in fact, the purpose for which he created us is the greatest expression of his love for humanity.