There are different styles of cover letter. You should tailor this to the type of job you are applying for.
Standard cover letter
Use a standard cover letter for sectors like business, law, accountancy and retail.
“Dear Mrs Smith,
Please find attached my CV for the post advertised [insert job advert location] on [insert date].
The nature of my [insert degree or course] has prepared me for this role. It involved independent research, initiative, self-motivation and a wide range of skills. An understanding of the [insert sector] industry was essential during my education.
I am a fast and accurate worker, with a keen eye for detail. I feel have the enthusiasm and determination to succeed in this role. I would be very grateful for the opportunity and I am available to take this position immediately.
Thank you for taking the time to consider this application and I look forward to hearing from you.
Creative cover letters
Creative sectors might find a 'standard' style of cover letter less appealing. They may prefer a letter that shows you have imagination as well as understanding what the job involves.
Speculative cover letters
A speculative cover letter can be quite different. You are introducing yourself and encouraging the recipient to read your CV. They may have a lot of applicants sending in CVs or they may not have any job openings. It's good to include a line asking to be kept on file if they do not have any available roles.