A business cover letter should explain why you are a good fit for the job to which you are applying. It ought to focus more on your personality and why you are a good fit for the company, rather than strictly on skills and experience.
Before writing a business cover letter, research the company to find out more about its values and business model. Mention some of this information in the cover letter, along with how you can contribute to the company specifically. Avoid humor in the cover letter, but do write it in an individual style that reflects your personality.