I'm always interested in how people approach writing lyrics vs music, and I find the music-first approach fascinating because it never works for me, and I'm jealous of songwriters for whom it does. For me, I almost always start with a fragment of text+melody and develop them both more or less concurrently. The idea of writing an entire song without lyrics (or at least without lyrics that you intend to keep) is completely foreign to me.
This is not intended as a dig, I just find it interesting how different people approach songwriting so differently.