For professional with <15 years of experience
 
A cover letter is an essential tool for selling yourself to a recruiter or hiring manager and staying top-of-mind with them. Suppose you take the time to write a quality cover letter to accompany your resume. In that case, you are demonstrating your passion for the position to the employer, which can help you stand out from candidates whose applications didn't include one.
Optimize your job search by using every tool available. 
 
A well-written cover letter will:
 
Impress employers
Show personality
Demonstrate suitability for the role
Showcase passion for the role
Build a relationship with the employer
Demonstrate ability to follow instructions