Wow, some bad advice being given in this thread.
The cover letter and resume should be attachments. If you want to put it in the body you can, but that just increases your chances of being screened out before even having your resume looked at. Some might argue that it could increase your chances, but you're taking the risk of the person who receives your resume pre-determing whether your email should be deleted immediately rather than being forwarded with the others (often it's just an admin person who screens the emails before the resumes even get to HR). If you want to be picky, your attachments should be in plain text form but that's a royal pain in the ass to do so Word is your next best bet.
If someone tells you to write a "form" cover letter, immediately start getting your advice elsewhere. If ever there was a "shred bin" red flag, form letters are it. If you can't take the time to craft a cover letter specific to the job you're applying to, well, employers won't take the time to bother interviewing you. It's an immediate and obvious tell that you're either a) lazy or b) cold calling your resume.
I can't begin to tell you how many times I've seen a person's resume immediately tossed due to a bad cover letter. When you see hundreds if not thousands of resumes, you can instantly pick out the form letters and toss them out. It's an easy way to cull the herd down to a more manageable number. And if you can't write worth a damn or don't use spell check, chances are your cover letter will be read aloud in the office where everyone will laugh at how inept you are. Trust me, I've seen it happen.
Not using form letters has absolutely nothing to do with what level of position you're applying for. If you're applying for a six figure senior management job, chances are pretty darn high that the traditional resume/cover letter will play a miniscule part of the hiring process. For those jobs you're usually already pre-selected. HR doesn't determine who they're going to hire for a senior management position based off a cover letter or resume.
Here's a tip if you ever need to submit a hard copy of your resume: print it out on a heavier stock of paper that isn't white in colour. Your resume will immediately stand out in a pile, both by feel and by colour.
Your cover letter and resume should not repeat each other. They are distinct and have two separate purposes. I'd suggest hunting around online or buying a cover letter/resume guide for advice.
Oh, and one last thing. Never spam people with your resume! Recently we've been getting spammed by some moron IT programmers who think that's how you get a job. Sorry losers, that's how you keep from getting a job!