Why write a cover letter?
Imagine you are a recruiter trying to fill a new position. You have a stack of 150 resumes to wade through to try and decide who is worth bringing in for an interview. It's hard work! You have to analyze the resume to see if the person has the relevant experience and skills. Then you come across a application that also has a letter summarizing why the person meets the requirements of the job posting. That person just made the recruiters life easier and is more likely to be picked for an interview. In fact only 18% of candidates include a cover letter with their application. Those candidates are more likely to be invited for an interview because (a) they stand out because they put in a little more effort and (b) they made it easier for the recruiter to find the relevant information. That's why you should include a cover letter in your application!
How to write a cover letter.
Start out with a generic greeting like "to whom it may concern." Avoid upsetting the recruiter by making any gender assumptions.
Next, begin your cover letter by letting them know that you are experienced in the job area you are applying for. This plants the seed that you are a whatever they are looking for.
Then tell them you would be great for the job because you can help solve whatever problem the business has in the job description. For example managing projects in time and under budget. Be sure to include the actual job title you are applying for. It is important to customize your cover letter for every single job you apply for. Never send a generic cover letter, it won't help your application at all and it may even count against you (recruiters can spot a generic cover letter a mile away!)
After that tell them that you really like specific roles in the job. For example budgeting, managing people, producing metrics. This tells them that you want this job not just any job.
Then call their attention to relevant skills you have listed in your resume. For example GAAP accounting or SQL server administration. This will make sure they go look for those details in your resume.
Finish off by mentioning something about the companies culture. Go to the "about us" page on their website and find a part of the culture or values they mention. If the company thinks its important enough to mention on the website then it is something they will look for in new hires.
Then sign off letting them know you can't wait to talk with them more about the position.
Sample cover letter
To Whom It May Concern:
I am a seasoned professional with a background in AREA.
I would be a great fit for the JOB position because my experience will enable me to help you start REQUIREMENT quickly. I have a passion for ROLE, ROLE and ROLE. You will also see from my resume I have a history of SKILL and SKILL. Lastly, I am a big proponent CULTURE.
I look forward to hearing from you soon.
Best regards,
Name
A career coach can help you craft a cover letter.
You might also be interested in reading: How to tailor your resume.