(If I met him, I'll tell him) is it Ok?
Is it correct? Because I've heard a lot of people say that.
Using If + past tense, + will (instead of would)

Thanks

Question

(If I met him, I'll tell him) is it Ok?
Is it correct?  Because I've heard a lot of people say that.
Using If +  past tense, + will (instead of would)

Thanks

Answer

This is called a mixed conditional, and you need to ask exactly why the speaker chose to start with a second conditional then finish with a first conditional.

If you understand the rules clearly for English conditionals, you'll be able to identify why the speaker chose to mix them.

Answer

This is not correct because it doesn't make sense with both a past tense and future tense verb. If you want the future tense, it should be:
"If I meet him, I'll tell him."
or 
"If I see him, I'll tell him."
where both verbs are future tense.
If you want the past tense, it should be:
"If I had met him, I would have told him."
or
"If I had seen him, I would have told him."

Answer

If I meet him I'll tell him.