Hey!

'I' when used as a first person pronoun, then it is followed by 'am'. Ex: I am a boy/girl.

And, to use 'I' with 'is' is grammatical impossible.

But when 'I' is simply used as a word, then it might be followed by 'is'

Example : I is the 9 the letter of alphabet.

I is the word used as first person pronoun.

Hope it helps!