Of all the numerous online metal debates I frequently encounter, perhaps the most perplexing to me is the common contention that Viking metal is not a real sub-genre. Below, I'll briefly cover my thoughts on a few of the various arguments I've heard in support of that claim.
"Viking metal is just ______ metal about Vikings."
The blank space in this one can be filled with any accepted metal sub-genre, but the most common ones are black and folk, though I've heard death metal inserted there too. I feel like I've said this a thousand times, and I'm sure I'll say it a thousand more but LYRICS DO NOT DEFINE GENRES. There is no genre or sub-genre of music which can be solely defined based on lyrical content. A good illustration is that Amon Amarth are a death metal band that sings about Vikings, while Moonsorrow are a Viking metal band that doesn't. Of course Vikings are a common theme in Viking metal (for obvious reasons), but there are also stylistic elements which separate Viking metal from those others. The pacing, musical composition, and general feel of Viking metal are entirely different from those found in the other sub-genres I've mentioned. Of course there are bands that blur the lines, but genre mixing artists have existed since about 30 seconds after the invention of genres. Just because it's hard to tell whether that old Enslaved album you're playing is black metal or Viking metal doesn't mean there's no difference between the two. Falkenbach still don't belong to the same sub-genre as Darkthrone. And for the record, they don't belong with Korpiklaani either.
"There is no such thing as Viking metal because Vikings didn't play metal. Their music was played on flutes and other similar instruments."
I'm sorry, but this is just a dumb argument. Surprisingly, though, I've heard it several times. Allow me to illustrate a basic problem, for those to whom it is not obvious. To do so, let's look at this statement by employing some parallels with other sub-genres, shall we?
-Vikings were barbarians. They did not play metal. Thus, there is no Viking metal.
-Black is a color. Colors cannot play metal. Thus, there is no black metal.
-Death is the end of life. That is not something with a tangible body, so it cannot play metal. Thus, there is no death metal.
-Thrash is an aggressive verb. Verbs cannot take action themselves, like playing metal. Thus, there is no thrash metal.
And so on and so forth. The fact that a musical genre or sub-genre is named after something that did not itself perform that type of music is no kind of argument against the existence of said genre or sub-genre.
"Bathory invented Viking metal, but they were the only band that played it."
Yes, I've heard this one. I think most of us can agree that to be a genre (or a sub-genre) there must be multiple bands or musicians performing a style of music. If there is only one band playing it, then it's not a sub-genre, it's just a unique band. And since you wouldn't attach a genre label to a single band's uniqueness in any other case, it doesn't work to do so here either. Yes, bands have tried to avoid being labeled by assigning themselves unique, made-up sub-genres. Alestorm call themselves "true Scottish pirate metal" and Verjnuarmu call themselves "Savo metal", for example. These are gimmicks, though, which are useless as real musical distinctions. At the point of making this statement, the speaker has basically already conceded that Viking metal is a real genre, and trying to then neutralize that by excluding everything except one band is just silly.
There are others, but these few spring readily to mind. If you couldn't tell (or if you didn't know already) I have a definite stance on this question. To be honest, other than the fear that there are too many sub-genres in metal, I don't even understand the point in making this argument. And if excessively narrow labeling is the concern, perhaps it would be better to go after "melodic symphonic blackened death metal" or something first.