Fills is what I call it. It’s not hard once you get the hang of it. I like to just “walk” the scale up to the next chord the guitars are are playing or walk it down the pentatonic scale. Sometimes just play the arpeggio and sometimes play it an octave higher. Mix it up so it sounds fresh without covering up the vocals and don’t overplay it. John is the expert so let’s see what he can offer.
Playing fills well can be more involved than just playing a lead break…you have to know both the chord progression and the timing of the vocals fairly well…playing with others regularly helps this a lot.