What is the difference between
I have to go
I must go
I should go
I need to go
I'm going to go
1I have to go 2I must go 3I should go 4I need to go 5I'm going to go 6I ought to go.
In order of need: (4 is a floater)
most needy 2, 1, (6=3), least needy
5 is different in kind from the rest = I will go. It expresses intention, not need.