To some of you, the thought of using a metronome may conjure up old memories of past piano lessons. If the experience was an unpleasant one you may have developed some negetive ideas as a result. Perhaps I can help to dispel any misconceptions you might have by explaining how a metronome can be used to benefit your guitar playing.
For those of you who have no idea what I'm talking about, a metronome is an instrument that is used for clicking off exact intervals of time within a given piece of music. The tempo can be adjusted to suit any relative speed that is suggested for a particular composition or exercise. They come in a variety of types and sizes too. Everything from a large wind-up, pendulum swinging metronome to a small, pocket-size digital one with lights that blink on each beat, are available.
As a guitar player, one of your highest priorities should be learning how to count time correctly. A metronome can work wonders in helping you to develop a more consistent rhythmic feel. It can be used to practice simple exercises (such as scales or licks) or help you to master a more complicated piece of guitar music, whether it be classical, jazz, rock or whatever.
When using a metronome, set the click on the quarter beat (or down beat) of the music. This will make it much easier for you to count the time. In other words, when using a 4/4 rhythm (regardless if you're playing quarter notes, eighth notes, sixteenth notes, etc.) set the click to sound four beats per measure.
It's usually easier to begin learning a new song by setting the tempo at a slower speed than may be indicated on the piece of music you're playing. This is especially important if you are new to using a metronome because it will seem a little weird at first! Setting a slower tempo will give you time to map out the fingering on the guitar and get used to recognizing the down beat. Be patient with yourself.
With a little practice you will begin to feel comfortable using a metronome. Be persistant and pretty soon you will notice a definite improvement in your playing. Afterall... it's just a matter of time
source: abclearnguitar.com