A covering letter should be seen as an opportunity, it is mostly required for permanent positions but in some cases it can also be useful for a consultancy role. The covering letter brings an addition dimension as it can join the dots between the current opportunity, your CV and other relevant details about yourself. This document must be tailored to each opportunity and written specifically for each role. It allows you to explain a few more things and underline your motivation to apply for a specific role, at a specific company to a specific employer. This letter needs to be tailored to be appealing.
Make sure that you provide detailed contact information !