Yes! Yes! Yes!
A covering letter of application or letter of introduction is very important. Why? Because a well-crafted covering letter will get the ‘big-picture’ and your ‘critical information’ across within two or three paragraphs (about 10-15 seconds), and engage the reader.
Statistics show that a job applicant has the first six lines (five to ten seconds) to make an impact. The covering letter is the best way to make that impact.