It is generally considered to be exceedingly difficult for a non-US citizen to gain entrance to a US medical school. Difficult but not impossible.
Conventional wisdom on the topic:
1) your best bet/chances are at private medical schools which do not rely as heavily on taxpayer/state finances to operate
2) be aware that some schools require foreign students to have documented proof of ability to pay for all 4 years of medical school in a secured account (ie, enough for tuition and living expenses)
3) US loans are generally only available to non citizens who have a US credit worthy citizen who will co-sign for them. Your home country may have other resources
4) very few foreign students will be offered enough scholarships or grants to pay for most of the costs and you will be expected to make up the difference.
5) MD-PhD programs are sometimes more open to foreign students.
Please do a search of this site for more information as this is a common topic on the boards from time to time.