Fixing any problems you have, whether it be sloppiness, bad feel, not being able to swing well, funk well, rock well or whatever well always comes back to your perception of and playing of time. If you don't perceive and feel exactly where the beat is, you're not going to be able to place your notes in the right space. And even more, you're not going to be able backphrase or play on top of the beat either -- at least not as a conscious choice. You'll end up dragging or rushing, which is not the same thing as consciously backphrasing or pushing in order to create tension.
When I was in college, the idea of playing with a metronome to many people seemed like the most school thing you could do-- that's not music, that's academic. It's what classical musicians do, not rock players or jazz players or whatever. In one of the first ensemble classes I had at Berklee, the teacher berated us, rightly, for our crappy time and told us we needed to practice with a metronome.
I remember thinking that was lame because first; I already had good time (right), and second I wanted to learn about more interesting things like hybrids and exotic scales. What I didn't realize was that no one would want to play with me if I couldn't play those hybrids with good feel.
So, for everyone who thinks that playing with a metronome is square, I'll let Metallica make my argument for me.
Check out James Hetfield's monstrous right hand technique in this video, especially when he's in the control room starting at about 0:16 through 1:15. What's that you hear in the background that he's playing with?
Don't take my word for it, Hetfield gives you permission to work on your time.