A cover letter should be used to accompany your CV. It allows your application to be more personal and highlight your strengths which may not be so clear in your CV thus impressing your employer. So remember, don’t copy a template as the chances someone else may have also done the same are not so slim.
The format should be clear. First paragraph should be set out why you are writing the letter & when you are available to start the role. It should be addressed to the person who will be reading the letter.
The second should be along the lines of what attracted you to the position and what you can offer to the company. It’s a great way to show your skills match the requirements on the job specification. This shows the company you read the application thoroughly.
Finally, your final paragraph should show why you’re keen to have a personal interview and how you look forward to receiving a response. Don’t forget to thank them!