Well, I remember playing MGS when I was younger and it had first came out, it was very cool then, but now if I played it I would say the graphics sucked. Haha. Honestly you can smoke, hide from enemies under boxes, and solve puzzles. I don't remember the story line, but for someone who wants to know the story, I would start with the very first ever made MGS game, being Metal Gear Solid. :)
For you to know, the history of the Metal Gear game, you will have to begin with the first Metal Gear game, which was released on 1987. The first game is known simply as Metal Gear and tells the story of Solid Snake a Special Forces operative. Check out en.wikipedia.org/wiki/Metal_Gear_Solid_HD_Collection#Metal_Gear for more details.