Pro tip: I never look at anyone's cover letter. Mainly just resume's.
What is the thing belonging to the resume that you look at?
Their experience. I recruit doctors, so I guess you could say it's different. I mainly make sure to see that they have their diploma, back ground checks, license checks, reference checks, and we make them go through like 4 different interviews before they come on.
Recruiters/HR ppl get excited when resume's fly in. My manager literally wants me to call on everyone of them, whether they're a good fit or not, just to network. It really depends on the position, but if your background looks like you're qualified for that position, you'll usually at least get a call for a brief phone interview.