If you are an absolute beginner at metronome playing. Try just smacking your lap with your palm in beat(synced) with the metronome(Start at 100bpm). Then devide the smacking so you hit your lap 2 times per beat. Then do both examples playing an open string on the guitar instead of smacking your lap(It should be bloody by now). After doing this for a while play a simple song to the beat of the metronome. Then it´s just to advance further on more difficult songs.
A fun thing to do is to play tripets(Yeah, it´s realy hillarius*s*), to do this devide every beat into 3.(Note: try this only after you have mastered the other 2).