Military background will not hinder you to gain entrance into medical school, on the other hand it will probably be an asset. I know of one school that does give preferance to vets (ETSU) if all other (gpa, mcat) are solid. Prior Army here.
I pretty sure it will help in the overall, at least to show you have a little life experience outside the highschool directly to college don't have much more experiences norm. By the way, go Army.
-always a sergeant and a future front line trauma surgeon hopeful.
Let me be the 4th person to say "Yes, it really helps" and add that it helps even more if you are applying to USUHS. At USUHS, the officers (doctors) seemed to be impressed with my leadership experiences... although I was only a reserve Army officer for 5 years, I did really well in Engineer officer basic course, and graduated from Sapper Leader Course (had some great stories to tell there ) and subsequently was accepted to USUHS. Although I ended up choosing DUCOM (the med school formerly known as MCP-Hahnemann), I know that my prior military experience really helped me stand out, both to get an interview, and thereafter.
Oh, they love ex-military! I'm ex-Army intel and my interview was 9/26 last year. All they wanted to do was question me about 9/11. What the heck did I know about that? I spied on the Ruskies in the late 80's!!! Now send over some Soviet Armed Forces and I might have a clue...