At this point, it's basically tradition: The last show of the year is dedicated to the loud, the fast, the heavy, the cosmic and the sublime. A.K.A., when All Songs Considered host Bob Boilen and I talk about metal, punk and a broad definition of experimental music. Maybe you've listened to some of these outliers in my Viking's Choice column or even on the podcast — they definitely stick out like a sore, headbanging thumb.