The purpose of the internship cover letter is to act as a kind of an introduction for your employer to look at before he reads your resume. If your internship cover letter is good it might do the job of getting the reader interested in your application. You don’t know what kind of a person is reading your cover letter. So, you should aim at giving your best shot at writing your cover letter. Even if your application reaches a person who is not impressed easily it might not have a negative impact on your application.
The cover letter should contain certain basic information that every employer should know about you. These details include the reason why you want to intern with the company you have applied to, why you think you would be suited for the job, and your past experiences and achievements. Do not go overboard with the explanation for these sub-headings. Make it simple, but firm. You do not want the employer to be confused about your reasons when he/she finishes reading your cover letter. But, you also don’t want to let him/her think that you are not serious about the internship or that you don’t want it as much as someone else who has applied.
The other details that should find mention in your cover letter is the duration for which you would like to intern with that company and the months you would be comfortable with. If you have a rough date in mind, but are willing to bend the rules if you are offered the internship you could include it in your cover letter.
Pay attention to the language of the cover letter. You cannot go wrong with the grammar. It does not create a good impression on the person reading it. If you are applying for an internship in the field of writing there is no scope for error. The reader might just take your cover letter as a sample of your writing and might reject you on that basis. Be careful about all these little things, which might have a big impact on your application while writing a cover letter.