OK. We are jamming and the guitarists say lets try something in the Key of G. So I am immediately harmonizing the Key of G as follows: G - I - major -Ionian A - ii - minor - Dorian B - iii - minor - Phyrgian C - IV - major - Lydian D - V - major - Mixolydian E - vi - minor - Aeolian (natural minor) F# - vii* - dim - Locrian Now where do I apply the scales and modes? In a rock/metal style? For example, while on the IV (C), I know I can play the root, root/fifth or the arpeggio/chord. But where do the scales and modes fit into this? I know that the chords are created from the major scale in this case. While on the IV (C), would I play notes from the C Lydian which would keep the notes all within the Key of G? Or would I draw my notes from the C major scale? If song called for me to wander into ii territory (Amin in the Key of G), would I draw my notes/inspiration from the A Dorian mode or the G major scale or simply the A minor scale? 00-0 0-0 D-00 or 0-0 0-00 D-00 A minor contains an 'F' as opposed to an 'F#' as dictated by the Key of G (overall key of song). So it is throwing me off a bit in terms of understanding where to apply scales and modes. I realize that nothing is set in concrete, but just looking for some guidance. Any help would be greatly appreciated.