There is no doubt about it: the introduction is important for any kind of writing. Not only does a good introduction capture your reader’s attention and make him or her want to read on, it’s how you put the topic of your paper into context for the reader.
But just because the introduction comes at the beginning, it doesn’t have to be written first. Many writers compose their introductions last, once they are sure of the main points of their essay and have had time to construct a thought provoking beginning, and a clear, cogent thesis statement.