There's not much ambiguity about that. Essentially, it's your first pitch for a job, contract assignment, or new business for your enterprise.
It is not a laundry list of your credentials. And it should never be your entire work history. If you're successful, you will get a crack at another pitch. That is, through the interview by phone, online or in-person.
Because cover letters are actually sales material, we all have to develop the mindset of the successful salesperson. If our way of pitching isn't getting the results we want, we have to re-think every aspect of how we are going about the sale. That's exactly what a salesperson does when in a slump.
As searchers for work, it's smart to review these:
What we're pitching for. We could be going after work we don't have top-notch experience in. Or the niche is glutted.
There's the old saying: We are barking up the wrong tree. At that point we might examine our skills and experience and figure out where they can be more marketable.
We are pitching to the wrong organizations. A startup in Silicon Valley isn't going to welcome us Baby Boomers. Maybe we are wasting our time trying to seek out a full-time job there. More receptive would be organizations which are more traditional and value our kind of experience.
The tone. Do we sound stilted aka old? Many of us developed our career path in old-line corporations. Yet, those doing the hiring never worked in those kinds of settings. They expect our tone to be conversational.
The content. The heavy lifting in a cover letter has to be to show employers that we are the best candidate to get the results they need. It's not to just indicate that we can do the work. Among the 300 answering that help-wanted, about 100 can do the work just fine.
Be specific how your experience can provide value to the employer. When possible, provide the numbers backing that up.
Use phrases like "the edge I bring."
If you can't emerge from your search slump, ask several professionals you trust to read the help-wanted and your cover letter. Beg for candid feedback. Don't become defensive. You lose nothing experimenting with their suggestions.