Metronomes are great for helping you work your way up through the tempos when you're practicing scales, leads or any difficult passage. With a metronome, you can set speed goals for your practice, and track your progress. You can also use a metronome to find the accurate tempo of a song.
If you want to download a metronome app, you might prefer one that has drum sounds, instead of (or in addition to) the traditional electronic metronome 'beeps' and 'clicks.' Practicing with drum sounds is more realistic than playing with a metronome.
With all of the metronome apps out there these days, this page is almost redundant. Anyway, here are some good-sounding drum beats at a variety of tempos. You can play the tracks directly from here.
4/4 Drum Beats
Roland 60 BPM
Roland 80 BPM
Roland 100
Roland 120
6/8 Drum Beats
(I don't have precise tempos on these ... )
Ensoniq 6/8 No. 1
Ensoniq 6/8 No. 2
Ensoniq 6/8 No. 3
Ensoniq 6/8 No. 4
Ensoniq 6/8 No. 5