Dan, welcome to the site dude. Vibrato is probably the most under-appreciated technique in guitar. It can make a dead note come to life with vigor. It's the subtle things like this that make the difference between being good and being great. My favorite guitarist is Steve Vai, who has excellent vibrato. Back in 1984 he did a mini-lesson on vibrato technique which you can find here. Take a good look at that article and maybe you'll come away with a good technique to use.

As for developing a great sense of rhythm, it comes with practice. Get some backing tracks off the internet and jam over your favorite songs until you feel really comfortable. It's good that you play with a metronome, definatlely keep that up. In time you'll have great time :D