In a dictionary, the verb ‘BE’ has a number of definitions and forms:
BE [verb]
be I am going to be watching the squirrels dance.
am I am watching the squirrels dance.
is She is watching the squirrels dance.
are You are watching the squirrels dance.
was She was watching the squirrels dance.
were We were watching the squirrels dance.
been They have been watching the squirrels dance.
Therefore you can correctly say ‘I am’, ‘she is’, ‘you are’, etc.
Is it ever grammatically correct to say ‘I is’?
July 14th, 2012 | Category: 
Yes, but not in the context described in the question. For example, “I is found between H and J in the alphabet.”
… or we could say, I is the ninth letter of the English Alphabet
Big Daddy got there first,
such as: I is the second letter in the word winner–and you are today’s.
I really liked this one!