The covering letter, or cover letter, is about your MOTIVATION for doing that job. Do not repeat all the information in your CV.

Open with an introduction explaining the job you’re applying for and attaching your CV, so they know exactly why they’re looking at it.

There then needs to be 3 paragraphs. 

1. Why you are the perfect candidate. 
2. A summary of the unique skills and experience you offer.
3. Why you’re excited about working for the company.

Demonstrate that you’ve done research about this particular company.

If there is one thing that can clinch the deal (above all else), it’s passion – employers hire individuals that love their job. So don’t be afraid of showing your enthusiasm.