just keep it super short nothing too long. I learned that people get annoyed by long intros no matter how well pieced together they are.
I always start
"Hey guys hows its goin, PepperBeef2Spicy here, bringing you some *X*" -> video
and then outro with "Thank you guys for watching, and i'll see you guys later"
sometimes i'll leave with an additional "have a good day" or what I will be doing the next video (if its a series). Short, sweet and to the point, this is one of those things where IMO thats the only way to go.
Is it necessary?
technically no, but I think its only beneficial.