well dude you don't gain weight by just eating. OK, here's a couple of tips from a football player. I'm almost 5'9" and i weight a little over 152, but my body fat % is only 4%. here are tips to gain weight:
1) eat, then eat, then go and eat, then go and eat some more. if you don't eat a fuckload, you won't gain weight.
2) to gain muscle, you need to consume AT LEAST 1 gram of protein for each pound of your body weight. if you don't, well good luck on gaining weight then.
3) EAT!!! START NOW!!!
4) lift weights. but don't overdo it or tire yourself all the time. if you thing that tiring is good well congrats you are a bullshitter. your muscle grows not in the gym but when you rest, sleep, or take naps. so the more you rest the more muscle you gain, quite ironically.
but still, do plenty of weights
5)GODFUCKINDAMMIT I DONT SEE YOU EATING SOLDIER!!!
6) but don't eat enough to gain fat instead of muscle, remember that.
7) no more than 2 pounds a week. be patient, and keep in mind that well, like 10 extra lbs will look GREAT on you and it only takes like a month!
so follow these simple steps and i guarantee you that you'll look like nothing short of bradd pitt or matt ratliff. and don't listen that bullshit about high metabolism, that the biggest fucking bullshit i've ever heard since britney spears, if you exercise, your metabolism WILL show down.