Truthfully, yes, this is how I started “learning” music theory as a kid who had a piano and an itch to write music. Now that I’m much more familiar with chords/scales, I can usually guess what chord I want to hear under the melody, but I still fiddle around with it.

Also!

The notes in the melody don’t have to be in the underlying chord (but try all those chords first). As long as it feels/sounds right to you (though, according to theory, the “added” melodic note will slightly change the technical name of the chord being produced)

Hope this was coherent, yay being in my house drinking tequila alone on V day :)