The aim of the covering or accompanying letter is to arouse positive interest on the part of the person reading it, to lead them to look at your curriculum vitae and to persuade them to offer you an interview.
The covering or accompanying letter is as least as important as the Curriculum Vitae.
In fact, this letter is your very first contact with your potential future employer and it must make them want to continue reading it, and hold their attention for long enough that they decide to look at your curriculum vitae, which comes attached to it.
You will understand that a poor introduction will not be without effect on the way your potential future employer views your curriculum vitae.
This letter is in a way your “shop window” and must create the desire to know more. So don’t neglect this aspect of things.
The covering letter is calling out something direct and precise; your potential future employer should see in it your motivation, your aims and your desire to be granted an interview. So it should at least give him a good reason to contact you.