> Techno and heavy metal have completely traditional harmony and rhythm.This depends very heavily on which subgenre of techno you're talking about. Melodic techno tends to use functional harmony, yes. But there is a lot of techno out there that has no recognizable harmony at all. It may have a root note, but bass and/or melodic lines, if present at all, can be completely chromatic.
Rhythm is almost always 4/4, of course, but it's hard to deviate too far from that with dance music. Within that, techno tends to do a lot of interesting polymeter stuff. Whether you consider that traditional or not is, I guess, open to interpretation.