What is the relationship between the melody line and the rhythm chords?

Question

Let's say I've written a song with the chord progression I-IV-V in the key of A (just as an example). So, the chords I'm playing are A-D-E. When playing a lead over this rhythm, what notes do I need to stick to over each chord? That is, when playing an A chord, should I stick to the notes that compose the chord? Are there rules for which notes sound good over which chords? When I move to D, are there notes I should avoid or continue?I'm asking because I have a melody I like and I'd like to back it with rhythm guitar, but I'm not sure how to choose chords (basically the other way around from how I asked the question, but I'd like to know both). I'm just starting to learn musical theory and I'm not sure the best way to phrase my question.

Answer 1

Each individual chord in a chord progression provides a harmonic environment that helps to suggest the musical mean of a melody. Each chord also provides at least 2 counter melodies; the highest and lowest note, in the chord voicing. The notes interior provide weight or color or additional harmonic definition. A harmonic rhythm is established by the frequency and rhythm in which the chords are played. The melody works with and/or against that rhythm to create a groove.

The whole point of music theory is to understand effective harmonic and melodic sequences. Don’t think of theory as a set of rules, but, rather, the history of what is known to work.