Indiooo
Member
Learn all the modes of the major scale, for starters, in one key. Learn their diatonic chords. Play around with it, listen to the difference in flavour, good melodies will eventually come to you. Being aware of the relative major/minor scales is also useful. Say you're in the key of D minor. D natural minor shares the exact same notes as F major, but the minor key is obviously darker sounding. This relation between natural minor/major scales allows you to modulate very easily between them, allowing you to play something dark or something a bit brighter only by changing the tonic, not having to worry if your modulation is going to sound harsh or abrupt. But back to the point, most melodic metal stuff is melodic minor all the way.