We are nearing the end of a study of a crucial era in our Church's history - the formation of Christology (that is, our belief about the identity and nature of Jesus).
Most of the early heresies were Christological in nature and were resolved largely at the Councils of Nicea, Constantinople, and Chalcedon (325, 381, 451 respectively).
Homework: identify, through independent research, the following heresies. Know who the proponents (leaders) and opponents were, the era (decades) in which it was most popular, and the regions in which it was strongest.
Modalism / Monarchianism / Sabelianism
That will do for now. Who knew there were so many wrong ways to understand Jesus?!