The snow monsters you are referring to is called Wampas. They are Yeti-like creatures that live on the sixth planet called Hoth. In the movie, Luke is captured by a Wampa and trapped in a cave completely updside down frozen to the ceiling. He is able to retrieve his lightsaber to cut himself loose and cuts the Wampa's arm off. 9 years later Luke returns to Hoth and encounters the very same snow monster with a severed arm and Luke prevails again by killing him. Without this scene, we would never have known or seen a Wampa or a massive snow monster!