To give your bass tone serious meat on rock and metal tracks there's little better than bass distortion to bring a ballsy fuzz or gritty edge to your low end.
Fortunately there's a huge range of bass distortions available, which cater for anything from a light grizzly tone to huge, crushing break-up. Ramp the gain up and blend it gradually into your dry signal to create the perfect halfway house, and to make sure that you still stand out in the mix while providing edge or wash depending on preference.
Some bass distortions double up with octaving effects for the maximum depth to your tone. As a bassist in, say, a three-piece band, it's the easiest way of filling out the mix, but also makes you a more formidable proposition when you're playing with bigger groups too.