Your friend is not an idiot, but you might seem to be if you don't do a little "self learning" on this subject instead of just asking for an answer on a silver platter. (yes I'm a bit of a jerk, sorry, think of it as tough love)
I recommend that you read any or preferably all of the handful of "druid tanking" threads that are on the main page of this forum at this very moment, especially the one called
Druid Tanking Guides and Links. Pretty self-explanatory. I recommend hitting the sticky while you're at it.
To throw ya a bone, druids are well known for being great tanks, especially being able to stand up to boatloads of physical damage with more armor and hp than comparably geared/level warriors, and for holding aggro on a single target better than warriors and pallies. Our bear form has a threat bonus just like defensive stance, and many of our bear attacks generate a lot more threat than the raw damage they put out. Prot-spec warriors are still acknowledged as the best end-game tanks because of the resistance plate gear, their ability to better deal with spell damage, etc., but it's rare to run into a party that isn't 100% accepting of, if not enthusiastic about, having a druid tank.
Edited, Dec 4th 2007 6:08pm by JeeBar