The answer is always YES! Why? It's your calling card. It's a tool to use in your job search that, if properly prepared, will paint a favorable picture of you to any prospective employer.
Typical contemporary resumes start with an Objective that clearly and concisely states what job you are seeking. This can be from a couple of words to a paragraph in length.
The body of the text describes your Experience, Skills and Accomplishments. These can be expressed separately, combined or in any combination so long as a potential employer can grasp what you have to offer with a minimum of effort. Listing specific skills and abilities, accomplishments, related training followed by a brief list of employers can be effective. Bullets can highlight this and make it easier to read. If you have been at the same job for a long time perhaps a brief descriptive paragraph outlining your skills, abilities and accomplishments would be effective.
End your resume with Education. Include professional seminars and training. Only include dates on recent items. Leave off High School unless you have nothing else. Don't give graduating date unless you specifically want them to know your age.
Maintain a current list of 4 to 8 references that any prospective employer can call. These references should know that they are on your list and you should have current phone numbers and/or addresses on them. These should be work related references. Former supervisors and coworkers are best.
Any time you mail a resume you should include a cover letter. The letter should be professional, brief and possibly include an indication as to why you would be of interest to the company you're sending it to.
Avoid generic letters. If you have a lot to say then consider adding an Introductory page after your cover letter. This is not a common practice but it does allow you to catch the reader’s eye with the cover letter, then lead them to read the detailed introduction.