I am getting into jazz harmony, so have recently started learning chords derived from the modes of the melodic minor scale. As far as I can tell, these modes are primarily used for two main functions:
making substitute chords to play instead of the basic chords from the equivalent ''normal'' mode- (eg playing a lydian sharp 5 chord, instead of a normal M7 chord). Or, creating chords that primarily work as V chords in normal keys, even though they are not the V chord of the melodic minor key. (eg lydian dom, altered, dorian flat 2).
using alternative scales to play over 'normal' modes, eg playing mix flat 6 instead of normal mix over a V chord for added colour.
So, for example, do lydian dominant chords ever function as IV chords? Do dorian flat 2 chords ever function as ii chords? The only chord derived from dorian flat 2 I can see talked about online is the dominant sus4 flat 9 chord- which again of course functions as a V chord. Likewise, I only ever see lydian dominant and altered chords talked about in terms of being used as V chords (and of course mix flat 6, but that actually IS the V chord in melodic minor). Regarding Locrian natural 2, I only ever really see this talked about as a substitute scale to play over half dim chords, or a mode to create locrian chords which have a major 9 extension. But again, this would be a variation on the vii/ii half dim function of locrian, NOT a vi chord function.
So apart from the triad-based classical music which uses melodic minor (and even in this case, the harmony is primarily derived from natural and harmonic minor), does the melodic minor scale ever work normally as a key?