Melody or a pseudo melody?
I just proved to myself (once again) that writing harmony first is going about it wrong way. Melody has to go first (most of the time).
Why? The ancient wisdom is that melody and harmony are the same thing, just looked from a different perspective. If you don't know what I mean, Google it.. Hence a melody shows all the harmonic possibilities, and harmony opens or closes the doors for a melody equally.
It's good to think about the core of a song first. Sure, it could be a rhythm, a chord, or even a sound or an effect. But what really makes a song unique and memorable is (almost) always the melody! It's melodies that tend to move people more deeply.
So, if you write a melody first, it's just a matter of supporting it properly later. You listen to the melody and you find all the chords that could possibly work. This approach is more natural than making a harmonic progression first and try fitting some notes in it that may (or may not) make a strong melody.
There are many musicians who don't understand this. And that's why the melodies of most of the pop music nowadays are really miserable. You couldn't sing them without accompaniment and not feel stupid about yourself...
Not that every melody has to be strong and independent! There's lot of potential in riffs and rhythms too. But at least you should be able to identify if there's really a melody present in a song or not. Is it a real melody or rather a pseudo melody that's really just some random notes (often just one or two notes) that happen to fit the harmony.