The quick answer — YES!
Although some recruiters and hiring authorities may skip over your cover letter and dive right into your resume, there are others who expect a covering letter or email message introducing yourself.
They judge candidates by what’s in that letter or message, and may dismiss you if you don’t send them one with your resume or other career documents.
Err on the side of caution and include personalized cover letters targeting each specific employer every time you send out your resume.
More information and a sample referral cover letter for a COO – Corporate Turnaround Management, read my Executive Career Brand post, Cover Letter Debate: Are They Necessary in Executive Job Search?