DC- Area metal band Darkest Hour performs at the annual Summer Slaughter Tour, at the 9:30 Club. Pictured: Aaron Deal, bassist, formerly of Salome. (Josh Sisk/FTWP)

Darkest Hour might be D.C.’s hardest-working band. For more than a decade, the heavy-metal quintet has been touring endlessly, both at home and abroad. It has played at Ozzfest and, quite possibly, in your neighbor’s basement.

On Monday night, the group delivered a energetic, if dutiful, 40-minute set at 9:30 Club, riding near the top of the Summer Slaughter Tour’s 11-band bill. At vocalist John Henry’s request, local fans rallied into a churning mosh pit, charging across the club’s floor to pound at one another in a brotherly but bruising way.

DC- Area metal band Darkest Hour performs at the annual Summer Slaughter Tour, at the 9:30 Club. Pictured: John Henry, vocalist. (Josh Sisk/FTWP)

Darkest Hour’s music is a hybrid of two severe subcultures — merging hard-core punk riffage with the shrieked vocals and blast beats commandeered from Swedish black metal. The tunes are complex, almost to the point of abstraction. Glassy harmonies zigzag into brutalist pounding. Darkest Hour has never mellowed out, but it has become increasingly tuneful over the years. On the group’s most recent record, “The Human Romance,” Henry tweaks his growl-to-melody ratio in the latter category’s favor, grumbling fully singalong hooks. And the band’s arrangements have become less claustrophobic, frequently indulging in spacious interludes.

Unlike its ax-wielding peers, such as Mastodon and Baroness, Darkest Hour is a creature of the rational world. While the lyrical imagery often calls upon the macabre — skeletons, pestilence, death — the sentiments lean toward social criticism and self-examination. On recent fare, like “Savor the Kill” and “Love as a Weapon,” the group even skews a bit emo. Still, it emotes at the highest possible volume. Darkest Hour may not be a wizards-and-warlocks band, but it can still bring out the devil horns.