Because most hiring is done by people who have better things to do than read form letters, I don’t use a cover letter unless I can find a good reason to write one. Good reasons include:
- The firm actually asks for one.
- I know who is getting the cover letter. It is much easier to make a cover letter meaningful if I can relate the text to the reader.
- The firm has a body of work that I am actually familiar with and am able to reference.

From these points you might notice that I object to form letters as cover letters. Always write a specific cover letter. Make it clear that you actually thought about why you want to work at a firm and that you are not just mailing them out to every firm in town. Something like “I am very interested in corporate identity design and want to learn to produce work like the stuff your firm did for companies X, Y and Z” is a good way to go. Name-dropping and flattery can also be good: “Professor and local AIGA president X recommended that I learn corporate identity design by interning for you because of your history of award-winning work in the field.”

thanks

I second James’s comment - you need to convince the design firm that you really want to work for THEM. Which means going on their site and educating yourself on what they do and customizing your letter to them. This was harder in my day, young man, when Al Gore hadn’t invented the internet yet.

I advise students to keep their cover letters brief; they are essentially a way to introduce your resume and convey your interest.
Hit a couple of key accomplishments from your resume, express your interest in the internship, and draw a connection or two between your work and the work the studio produces. But again, keep it short.
Above all, inject a sense of your enthusiasm about the field in general, and your willingness to learn as much about it as possible.