Udyr can be played in many different ways.

I use this guide every time playing 3 vs 3 ( didn´t play 5 vs 5).

He´s a very good pusher and can save mates very good.

especially against enemies wich fight in close combat my udyr is the best champ you can choose.

Also he can beat more than one enemy at once.

If you want to gank rush with bear stance than stun him and use phoenix stance.
After that look at your health bar and decide if you use phoenix stance again or turtle stance to refill your health and mana bars.

If youre ganked or attacked first use phoenix stance to damage your enemy than bear stance to stunn and then turtle or phoenix stance (look at health bar).

If a mate is attacked use bear stance to stun the enemy and make him flee with using phoenix stance.

Udyr´s Items focus on armor, but that makes him very resistable the whole match.

In plus he can deal a lot of damage with items increasing his attackspeed and damage at once like Madred´s Bloodrazor.

+ Udyr is very good in teamfights but also 1 on 1 or against more close combat enemies.

-Your teammates can ks your kills easily :D

+Udyr is a brilliant gank and protector and pusher.

Udyr´s masteries focus on defense to support his resistance in teamfights.

Udyr can be used as gank, pusher or supporter using my guide.

So hes one of the best characters in game, but if you want to kill many enemies like 20+
he isnt the right charakter for you