A cover letter is a tool to market yourself so it is quite evident that it will deal with you. Still, it would be wrong to assume that you should focus on yourself. Quite the contrary: you should write from the recruiter's point of view and stress what you have to offer to a company (not what a company can do for you). Use an interactional perspective and stick to the content of the job ad in your letter, without copying the content literally.

You'll naturally use the pronoun "I", but you should avoid an overdose of it. You can turn to "me" and "you" or "your company" from time to time. Do not start each paragraph with "I".

It is always beneficial to use information from the corporate website or from other sources. Some concrete details can show that you are not the focus, but the company is.