What is the grammatical problem with this sentence? [closed]

I need to leave early because I will meet a friend for lunch.

The above sentence is not grammatically correct but I cannot tell exactly what the problem is. Is it the usage of 'will'?

Thank you.

Solution 1:

I see nothing at all wrong with it grammatically.

It's not quite idiomatic because of the "will": it would be more natural with "I am going to meet" or "I am meeting", as those are more often used when there is a definite intention.

Solution 2:

It's not really ungrammatical, but it's rather odd. The reason for your leaving early must have to do with when your lunch meeting is scheduled, but the sentence doesn't really say that. Maybe this would be better: "... because of a lunch date with a friend."