The journal's guide for authors presents the guidelines on how to write an article for submitting it to that journal: how to include footnotes, how to number the figures, what style to use for the reference list or bibliography, etc.
The guide for authors should be the first thing you read before writing your article. Following the journal recommendations increases the chances that your article will be accepted and published.
For example, consult the section Information for Authors of the IEEE Transactions on Antennas and Propagation.
The structure of a scientific paper may vary from one field of engineering to another, but generally consists of the following parts:
At the beginning of the article:
In the article body (according to the IMReD template):
At the end of the article:
At Polytechnique, Professors Daria Camilla Boffito and Gregory Scott Patience have been working on the issue of scientific communication. They published a questionnaire entitled "How do you write and present research well?" in the Canadian Journal of Chemical Engineering, followed by a series of articles answering each question and offering writing tips.
How do you write and present research well? Answers to the 20 questions (includes a brief discussion):
Consult all the articles in the series.
The journal Nature discussed the work of Professors Patience and Boffito on the practices of assigning authorship in the article Who gets credit? Survey digs into the thorny question of authorship. Also read the Polytechnique news on the subject.