[Rudy4]

"Drums and bass" ARE the rhythm section in the context of modern rock. If a bass player doesn't want to focus on supporting song structure there are plenty of creative ways to play outside of that role.

Be aware that if you have need to be THAT bass player that some of us jokingly refer to them as "frustrated lead guitar players". Playing melodic bass is the classic "jam killer" in many band situations.

More mature players who work ensemble usually grow out of that and figure out their support role.

I love to sit around and play melodic lines on my fretless, but if I'm playing in a band situation then I change my M.O. to something that fits rhythmic support. If you're playing bass in a band situation that doesn't include drums then you ARE the rhythm section.