A metal crowd moves on the quarter note, and the thing moving it is your right foot. The headbanger groove is built to do exactly that: kick on every quarter, snare on 2 and 4, hand on every 8th, usually a china for the trashy bite. Nothing in the bar is left empty. Every 8th has a sound, every quarter has a kick, and the bar never stops driving. Where the power groove marked the pulse with one hand stroke per beat, this one fills every gap between them. Exercise 1 is that engine at ♩ = 110.
The texture lives on the downbeats. Count 1 & 2 & 3 & 4 &: on the four numbers the china and the kick fire together as one thick composite attack, and on the four &s the china is alone and thin. Fat, thin, fat, thin — that alternation is what a crowd nods to. Let the foot slide a hair off its china stroke and the composite splits into two separate events, the downbeat stops being a landmark, and the groove goes soft with every note still in place.
Making the kick and the china land as one attack
Build it foot first. Play the four kicks alone against the click at ♩ = 110 until they sit dead center, then lay the china 8ths on top without letting the hand renegotiate where the beat is. The foot is the reference here; the hand only has to agree with it. Add the snare on 2 and 4 last. At 110 that hand is turning out 220 strokes a minute for the length of a verse, so get the grip loose before you get it fast.
Exercise 2 doubles the hand and moves it to the hi-hat: straight 16ths, alternating R L R L, foot still planted on every quarter. Only one hand stroke in four now has a kick underneath it, so there is more hand between the anchor points and the foot gets less help holding its position. The tempo drops to ♩ = 100 for the wrists, not for the feet. Watch for the busy hand dragging the foot along with it. If the kick starts arriving a fraction early, stop, play the four quarters alone again, and rebuild the 16ths from a slower click.
Two ways to mark the last 8th of the bar
Exercises 3 and 4 both mark the last 8th of the pattern, and they use different limbs to do it. Exercise 3 is Exercise 1 with that final china stroke written open: give it a full ringing stroke and let it carry over the barline, and the band hears the bar turning over before it turns. If you have switched the hand to the hi-hat, the same marking is a lift of the left foot off the hat pedal on the & of 4. Exercise 4 leaves the hand plain and gives the job to the kick. At ♩ = 105, bar 2 ends with an extra stroke on the & of 4 that splits its last quarter into two 8ths, and over the full two bars that is the only place the right foot steps off the quarter-note grid.
Three things break this groove. Rushing is the first, since a pattern with no rests gives the hand nothing to fall back into and creeping ahead feels like commitment. The second is the off-beat 8ths swelling until they weigh as much as the numbers. You never have to accent the downbeats here, because the kick is already doing that for you; keep the hand strokes even and let the foot supply the difference. The third is playing Exercise 4 as two bars instead of one 8-beat phrase. Loop it until the push on the & of 4 feels like it points at bar 1 rather than finishing bar 2.