The main purpose of an Argumentative Essay is to persuade the audience into understanding their side of the argument; or in some cases, getting them to agree with it.
Here is the basic structure of an Argumentative Essay:
I. Introduction
II. Body Paragraph 1
III. Body Paragraph 2
IV. Body Paragraph 3 (Rebuttal)
V. Conclusion
The Rebuttal paragraph is the only difference in structure between a normal five-paragraph essay and an Arguementative one.
Happy writing!