If you are a college or university student, then your best bet is to find out what your college/university wants from you when it comes to essay structure. There is unlikely to be a single method that covers all your bases in a college/university unless you are in something such as law school, medical school or business school. You will be marked down in your college/university (sometimes severely) if you make a mess of your essay structure.
There is a reason for a uniform structure
If the essay structure is uniform and consistent, then it makes the whole process of reading the essay a lot easier. It also means that you can hop from one essay to the next without having to readjust for a different essay structure. It also makes referencing and showing evidence a lot easier to both do and understand, and it allows you to disseminate information in a more even-handed manner.
You are organizing information
An essay is partly about getting the information down and partly about making it something that a reader can understand. If it was all about information then people could make very long bullet point lists, or could simply submit their raw data. There is a need to create an understanding within your essay. There is also a need to conform to the norm. People have certain expectations when it comes to essays, to the point where defying conventional essay structure may cause undue confusion.
The basic essay structure
If you are talking high school level, then you are simply going to have your
Slightly more advanced papers may include thesis statement near the front of the essay. Even more advanced papers may have a research portion, raw data portion, a pre-amble other than the introduction, end notes, analysis and evaluation sections too.
Essay specific structures
There are many papers where a certain structure is expected. For example, an argumentative paper is expected to have one of two structures. The first may be a structure where lots of arguments are made and then lots of counter augments are made. The second may contain an argument, a counter argument, an argument, a counter argument, and so on. It is also possible to show a counter argument and then a counter to that argument itself.
There are numerous other essay types that have their own structure. For example, a cause and effect essays is expected to have a narrative timeline. This doesn’t necessarily mean that things have to follow chronologically, but more that events are shown to have consequences and repercussions that may be linked one to the other.
It is up to you as to if you use them, though it is not uncommon for people to set out topics, research, themes, etc, in the same way you may see chapters of a book. If you feel that adding headers to show the topic/theme of your next essay section then it may be worth adding them. Remember that they are added in order to aid understanding and not as a way of making your essay look fancy.