Michael the Archangel, for example, is known for being an expert in protecting Christians against evil, temptation and harm. As such, when you need protection Archangel Michael is a good angel on which to call.
In another version of the Leviathan myth, the creature was an angel serving under the archangel Uriel. When Satan rebelled and challenged authority in heaven, Leviathan joined him and was thus banished from heaven with Satan.