This advice was found on a LinkedIn post; I totally agree!
The cover letter should accompany the resume, and its importance cannot be stressed enough. While it may be true that some hiring managers do not read cover letters, send one anyway. After all, you do not know into which group your targeted hiring manager falls. In their book Cover Letter Magic, Wendy Enelow and Louise Kursmark explain that in a cover letter “you can pick and choose the skills and qualifications you want to highlight in each letter based on the requirements of a particular position. Cover letters give you the platform to create a vision of who you are that relates directly to the company’s or recruiter’s hiring criteria…” Thus the purpose of the cover letter is to introduce yourself and clearly define who you are; to highlight your most notable qualifications; identify the value you bring; capture your reader’s interest in you; and motivate the reader to read your resume and call you for an interview. You must send a unique and personalized cover letter with each resume you send out; no “To Whom It May Concern” here. If you don’t know the name of the person, there are ways to find it out, but you must personalize the letter and its contents.