Heavy metal music has definitely become more popular in the 2000's and 2010's, at least in terms of bands with commercial sensibilities.
True, but in the overall scheme of what genres are popular - at any given time - where would that fall? You may as well ask what
food is popular? It depends on the demographics of the responders: age, gender, locale, even era.
Popularity isn't perhaps too hard to define, any kind of music from any era is popular with someone, somewhere. But what genres and era are
most popular in terms of a correlation with the drummers playing them?
There'd have to be a specific definition about what popular means, or, select a genre. Actually, Metal is ideal, because drumming-wise, it evolved from rock into some specific styles, particularly involving double kick footwork.
That should be the new subject of the dissertation: "The Evolution of the Virtuoso Drummer Within the Metal Genres"
That would be pretty easy and interesting to trace, although one would also have to define the first bands and songs that were considered Metal.
Hmm, how about "Getting Musicians to Agree on the Definition and Origin of Musical Genres" It can be all about taking a survey, and the resulting varied and often conflicting responses!
Bermuda