Always follow your teacher's guidelines for an assignment, but this document can help provide some general information on introductions. The examples are informal or personal writing, but can be adapted.
This is a student example of a Metacognitive Response, specifically for Shared Inquiry. Notice that the student clarifies her ideas, but the focus of the essay is on her learning and process, not content.
If you have a specific question and you want a specific answer that you can actually understand, this is the website for you. It breaks down the rules of grammar in simple pieces, addressing the common errors and questions we all have. Mrs. H references this site all the time.