Here’s what you should leave out:
Old band members
Anyone who has been involved in your band a years ago or how you all met should be left out. Except, of course, if you want to publish a Wikipedia article about you or if someone became a star after leaving the band. Moreover, it is much more important to mention the current band members.
The complete founding history
You met your drummer in a bar? Great, but nobody cares. Unless you’re in a detailed interview or if you introduce yourself and get asked how your paths have crossed. So take a moment, and pick the most important facts of your story.
Too many awards
Ok, it's cool, if you have already been with XY on the big stage or have already recorded a song with XY. And of course, it’s also important to tell people out there. But your bio can quickly turn you "success" into a pure chaos and risks to become boring. So maintain a certain balance. Add only the most important events with real wow-bangers.
Don’t use “I”
Even if you are a solo artist, your bio should NEVER be formulated in the 1st person singular. Instead, write about yourself in the third person. This way you can stay objective.
These are e.g. the life stories of each member of the band. Or to beat around the bush, on the topic of how great your music is, rather than make it a short and crisp description. So get to the point! In addition, avoid mentioning countless influences that characterize your music. If you are not sure of what's necessary and what’s not, then ask yourself the following question: "Does it really add value or am I just filling a gap and avoid the essential information?"
Your band-bio should radiate with personality and individuality and bring out the best moments of your career.