This probably goes completely against what you have read on forums or being taught by other guitar teachers. We have always been taught that practising with a metronome is the best way to practise and it helps to improve ones rhythm and sense of timing. But I beg to differ and always advice my students to practise without one, specially during the early days of learning guitar. 

Instead of using a metronome, I recommend learning the art of tapping the foot while playing/practising the guitar. If tapping is not preferred, then bobbing the head or moving the body, something to embody the whole rhythm instead of using an external tool (i.e. metronome). Guitar players like Tommy Emmanuel and Paul Gilbert have always stressed on the importance of tapping in several of their interviews and/or guitar lessons. This is much harder than what it looks and a fairly difficult thing to master. But once it has been mastered, the timing of ones playing becomes so much tighter.

Metronomes are certainly useful when one is trying to improve the speed or breaking the plateau. But having a dependency on that is not the best way to become a better guitar player.