In a longer article, in the introduction, authors use to highlight features of the article that make it worth being read. Consider that the reader has potentially dozens of other articles to read, be it online or already stored somewhere in the HD. That could be one or more of the following items: a) the problem (complex, relevant, innovative); b) the state of the art (too many; too few contributions; promising); c) the purpose; d) the strategy and methods of collecting and analyzing data (innovative; unique; time-consuming); e) the resources (team; equipment; budget) and f) the results (positive, promising, surprising).
Several journals and conferences, however, consider that an introduction should be the proper place to summarize a) the problem b) relevant and recent contributions to solve it c) the purpose of the article: what author(s) intended to do. Each of these topics can generate a paragraph, so that a 3-paragraph introduction became usual.
The function of the Introduction is to establish the context of the work being reported. This is accomplished by discussing the relevant primary research literature (with citations) and summarizing our current understanding of the problem you are investigating; tsate the purpose of the work in the form of the hypothesis, question or problem you investigated; and briefly explain your rationale and approach and, whenever possible, the possible outcomes your study can provide.
The following papers in addition to the link (see discussions/referred publications) may further help.
Bavdekar, S. B. (2015) Writing Introduction: Laying the Foundations of a Research Paper, The Journal of the Association of Physicians of India, 63, 7, pp. 44-46.
Varadarajan, P. R. (1996) From the editor: Reflections on research and publishing, Journal of Marketing, 60, 4, pp. 3-6.
What are your tips to writing a good introduction of a scientific paper : https://www.researchgate.net/post/What_are_your_tips_to_writing_a_good_introduction_of_a_scientific_paper