Most people start off their cover letter by stating something like, "I saw your posting and I am very excited to apply." Not only is this generic, but it also does not entice the employer to continue to read your cover letter. If you want to tell them what job opening you are
applying for, just put Regarding: <name of position> above your salutation.
A hiring manager looks at a cover letter for an average of 3-5 seconds, so you shouldn't summarize all of your skills and career experiences if you want to stand out. You need to start right off by saying, "This is why I feel connected to your company, and this is what I can do for you as a business-of-one."
Do not just repeat information you already have on your resume. Since you stated why you're passionate about the company and what you can do for them in the opening paragraph, now it's time to provide some proof statements.