The orthodox formulation of the trinity wasn't declared until the Council of Nicaea met in the fourth century, and the word 'homoousios' was only barely included, in a last minute stroke of brilliance by one of Emperor Constantine's advisers, Hosius of Cordoba.
(Note: Picture = Not the Trinity in question.)
Likewise, most Christians today, in attempting to explain the Trinity, will resort to metaphors that are essentially heretical. Using the three forms of water - ice, liquid and steam - to explain the Trinity does not explain the orthodox conception, but rather an ancient heresy called modalism.
With those two facts in mind, I sometimes question whether the concept of the Trinity is a deal-breaker for Christian orthodoxy. I'm not arguing that it's unimportant, but I'm not convinced that it is critical either.
What do you think? Is it important for Christians to be able to articulate the Trinity in orthodox terms? Is it important for Christians to believe in the Trinity at all? Are Christians who believe Jesus was God's first creation, rather than co-eternal with God, hell-bound? Is the Trinity really important? Why or why not?