What heresies have arisen regarding the Trinity?

Throughout church history, various heresies have emerged that deny the true nature of the Trinity. Modalism, for instance, posits that God operates in three modes rather than as distinct persons, leading to confusion about the relationships and operations of the Father, Son, and Holy Spirit. The oneness movement, arising from figures like R.E. McAllister in the early 20th century, continues this error, insisting that the Father and Son are not distinct. The church has consistently refuted these teachings, emphasizing the necessity of acknowledging the distinct roles in the Godhead to maintain the integrity of the Christian faith and the gospel.