Yeah, you can do research in the military, the DOD is one of the largest providers of research funding.
That's not really how it works.
In order to be involved in a lot of that stuff you need to have had a security investigation, be read into programs and undergo a lot of expensive training. You don't just show up and say you want to work on something.
That money goes to industry, universities with National Lab partnerships, Ft. Detrich, Ft. Devins, Aberdeen Proving Grounds, Dugway, etc. The last two do chem stuff. You don't even get near the fence line without a clearance and a reason to be there.
When you are in the military, you don't pick and choose what you want to do until you've picked up some rank and are past your minimum service obligation. Most of your time will be spent in residency, various training events or on a basic GMO (General Medical Officer) or post-GME utilization tour. Then it's likely you'll be out of the military and looking for a job in your specialty, unless they put you in a GMO slot, in which case you're in the Match. The people doing research for the DoD aren't MDs/DOs. That's not what the armed services need MDs/DOs for.
OP, just get into med school, get on HPSP, do local, accessible research while you're there, get published if you can. Your summers will be spent training at places like Ft. Sam Houston learning how to do basic field medicine stuff.