Cover letters can be tricky.

For those of you who struggle with what to include, think of your cover letter as an opportunity to tell one story.
Pick a bullet point from your résumé that deserves more in-depth discussion, and use your cover letter to tell the story of how you solved the problem, came in under budget, completed a project ahead of schedule, or increased market share.
Let your personality shine in your cover letter. It’s your chance to share your success story and tie it back to the hiring organization.
This is yet one more way you can ROCK YOUR RÉSUMÉ.