Some journals will provide information about what to include in your cover letter in their instructions for authors. If no guidelines are provided, make sure you are probably introducing your work to the editor and you can also take this opportunity to explain why the manuscript will be of interest to a journal's readers, something which is always as the forefront editors’ mind.
The cover letter is changing with respect to the journal. It covers the paper contents , states its originality and establish that the article obeys the rules and regulations of the particular journal.
Some journals will provide information about what to include in your cover letter in their instructions for authors. If no guidelines are provided, make sure you are probably introducing your work to the editor and you can also take this opportunity to explain why the manuscript will be of interest to a journal's readers, something which is always as the forefront editors’ mind.