Dangerous Nonsense is one of those bands that most people struggle to describe, then end up referencing some kind of metal. There may be some of that inside the classical rhythmic structures the group employs from time to time — but its mixture of performance art, radical feminist and anti-capitalist lyrics and outsider post-punk is more akin to Poison Girls, the Raincoats and Crass. And this comparison is not made because the band is female-fronted or because of some other lazily observed, superficial fact. Rather, Dangerous Nonsense (due at the Oriental Theater on Friday, December 16) embodies the same spirit of experimentation and political awareness that informed the music of those other acts. That, and the fact that this trio seems to perform its music with a glee perfectly suited to its often vitriolic lyrics.