Do not regurgitate your CV. Instead, be sure to personalise each and every cover letter (and CV) for the specific role you are applying for.
The purpose of a covering letter is to address the ‘why me’ by highlighting your salient skills and experience, and why your character and personality makes you a great fit for the role in question. This is where you get to shine. Use the opening paragraph to explain why you’re writing to them and what it was that drew you to their company. Highlight the keywords in the job advert and as succinctly as possible, explain why you are the right person to carry them out.
Give examples from your career when you have done similar work, show them that you have the skills they are after and explain to them why here and now this role is ideal for you. Demonstrate that you are genuinely excited by this role – even though you might well be applying for lots of jobs, your cover letter needs to signal that this position is the only role that you are pursuing at the moment.
You can use the Star method to help you build a strong case for interviewing you