When you are writing essay it has to start with an introduction?

Essays don't always need introductions, but wouldn't it sound weird if you just leaped into talking about it? For an effective introduction, you want a hook, brief explanation, and thesis. The hook is to grab your readers attention, and should be fast-paced, exciting, or shocking. The brief explanation is to give some background for the other paragraphs, perhaps a definition or explanation of the subject you will go into detail later. The thesis is to sum it all up or to give the reader a little picture about what's going on, it's like when you have a puzzle an there's a picture on the front, it doesn't have all the pieces outlined and detailed, but it shows how it'll all fit together. The most important parts of this is the Thesis, but the other parts are important as well.