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

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?

Play A major chord. What are the individual notes within the chord? What if you play C against C#? There is a clash C against C#, right? What if you play D against C#? There is also a clash D against C#, right? But D against C# is most popular, and C against C# is not used as much. However, there is nothing wrong using such notes against other notes. The taste is up to you. Therefore, experimentation will be your best friend. However, there have been music composers and arrangers who used the notes both ways in the past. The best recommendation I have is to start avoiding the clashing of notes first. THEN...experiment with the clash and see how the notes will work for you.