Not if your resume is bad. Covers letters are a nice differentiator if your resume is good, so focus on making a solid resume first. Using this resume template and the advice in it is a great start to having a good resume.
Only after you have a strong resume should you worry about a cover letter. The truth is HR will never read a cover letter unless your resume is strong and they already think you can do the job.
I’ll put it this way: your cover letter can’t save you from a bad resume. If the resume is bad, nobody is going to waste a single second of their time reading your cover letter. HOWEVER, if your resume is good, a high quality, short (never more than one page), original (never cookie-cutter), company- and job-specific cover letter can improve your odds, show you did your research and are truly interested in this specific company, separate you from similar applicants, and make a great first impression.
I have a template and an example here, which you should definitely check out.