Depending on the journal, you may be asked to provide a very short Biography, but you have to pack a lot into that paragraph, and there won't be much space for a listing of your life experience. Only provide if asked.
I agree with the previous respondents. And I would add, that the separately stated expertise might be perceived as a compensation for weaknesses of the article. The short author bio is the place to mention relevant author info, unless other experiences are requested by the editors.
Usually the cover letter is not the right place for that: there, authors usually explain what the paper is about and why it should interest the journal's audience. Some journal editors ask authors to submit a short paragraph about their interests and publications after they have accepted their paper: you can mention your expertise then.