Watch the Chords in Melodic Minor online guitar lesson by Richard Hallebeek from Chord Creativity Guidebook
The melodic minor scale is a scale that can be used over altered chords. These are 7th chords with alterations, like a 7th b9/b13 chord. You'll also hear this sound on some of those "weird" chords you'll find in jazz and fusion, like Maj7#5 or maj/min 7th chords. In this scale, you can find many nice chord voicings that you can use over altered chords or the other chords I mentioned.