As said, the cover letter is very important. I recommend finding out the contact details of each person before addressing them. We'd throw out any addressed to "To whom it may concern" or "Sir/madam". Anyone who couldnt pick up the phone to find out who to properly address applications to was wasting their and our time.

The cover letter is where you differentiate yourself from your competition. CVs are a list of skills & experience. The cover letter is where you tell the prospective employer how your experience is going to benefit them.

a tip for all letters: use active voice, not passive voice. Instead of "I am writing to apply", which is passive, use "I write to apply". Google active voice if you need to.