I've had a few requests from members(including some members who haven't even posted any messages yet!) to join the Bronze Members group. Bronze Members isn't really a group, it's just a member ranking, along with Silver Members and Gold Members. Members who graduate to these ranks do not have any access to any additional features or additional sub forums or anything.
Bronze Member - requires 25 messages posted.
Silver Member - requres 50 messages posted.
Gold Member - requires 100 messages posted.
Hope this explains how the member rankings works.