Ach du liebe Zeit!!
"bpm" (beats per minute) usually means the quarter note pulse. And normally with a groove
pattern the snare hits fall on the upbeats 2 and 4. And if you play 8th notes on the hihat, you're
playing twice as fast as the metronome counts.
But of course you can always look at the pulse the metronome gives you in different ways,
especially for practice reasons. You can see it as eight notes, or half notes, even whole bars,
or advanced ideas like every "and" of the measure.
If I want to play a groove at 170bpm and I set the metronome to that tempo do I play every click or play at twice the speed of the clicks if it is an 1/8th note 4/4?
My reasoning: if it's a 1/8th note 4/4 then the 1, 2, 3, 4 are the beats and the 'ands' are not, but I'd still play them, for eg, on my hi-hat in a 170bpm groove. In other words my stick would be moving at 170 x 2 (that sounds a lot doesn't it? ).