as far as advancing the art of music goes, jazz and metal have made great strides. both have become havens for virtuoso musicians and creative innovators. deciding what types of music are 'interesting' or 'innovative' is hard to do and just depends on one's subjective impression of the music within the culture they're set in. maybe a more objective approach is to decide what forms are most 'unique' as compared to whatever style is statistically most popular within a given culture. either way, jazz and metal are among the highest echelons of music.
the real flare is the 'progressive' nature of these genres. could all jazz be 'progressive blues' and all metal 'progressive rock', abstractly?
jazz is - improv, polyrhythms, interesting rhythmic patterns from drummers and players in their notes, complex harmonic ideas, ambiguous rhythms, swing feel, groove prioritized in (a) the head and (b) memorable quotes in solos
jazz fusion is (borrowing from funk, rock) - electronic, groove, followable beats, followable riffs, more conservative/followable rhythm guitar/accompaniment, more/consistent high hats, audible kick, distortion, synthesizers, ambiguous and uncommon drum rhythms/time signatures, Complex harmonic ideas with more straightforward (if varied) rhythms
noting jazz fusion words, the corollary between them and modern prog metal is interesting. metals main innovation now is rhythmic variation, and secondarily adapting harmonic complexities of jazz. also complex 'arrangements' are important.
metal is not defined by distortion. its defined by either/or of the two extremes of rhythm: (a) groove, or oppositely, (b) chaos. a tight chunky groove is metal af, same as how complete arhythmic chaos is metal af. metal is usually one or the other and often mixes both. but distortion is not required.
modern metal has lost the need for distortion. 'heaviness is in the hands' - metal is groove which comes from rhythm and syncopation, no matter how complex or chaotic it is - and extreme chaos is just as metal. modern metal is complex but rhythmic grooves blended with interesting harmonic content: tigran hamasyan, chon, sungazer, car bomb, the algorithm.
to do something new, upcoming musicians will continue to expand these areas. anything less will be rehashing old ideas. as jazz evolved it became more harmonically complex and improvisational until it cumulated in free jazz. the most interesting new metal will follow a similar path.
