Mike Moxcey in Colorado writes:
If you're just starting out, turn off the metronome.
It is a far more useful tool for intermediate/advanced players. It can give you a rhythm to explore syncopation over the top of and can get your bluegrass roll timing down exactly correctly.
But it's just one more thing that gets in your way when you're starting out and trying to learn chords and stuff. Read Wernick's BNL column last month for a second vote.
I personally think a metronome is counter-productive because 1) it takes time to learn to use properly, time that would be better spent learning proper chord formations and far worse, 2) it trains you to listen to the metronome instead of to yourself.