The lights are on
I would strongly advise playing all of the Metal Gear Solid games, not just 4 (unless you already have). 1 is available through PSN; 2 (the best in my opinion), 3 (second best, again, in my opinion), and Peacewalker (worst, but it was a PSP game so it is forgivable) are all available on the HD collection; and then 4 is separate. While it is not necessary to play them all in order it is probably the best way. I have many friends who played only 4 and regretted it, there is a deep story that can be confusing if you jump in at the end. Not to mention they're all amazing games and among my favorite of all time.
If you do heed my advise, play Peacewalker last, it is pretty inconsequential to the story and after playing through the first 4 chances are you will be burnt out on stealth games for some time.