Building Muscle

I see two things stated here a lot and they seem contradictory.

1. You cannot build muscle on a calorie defecit

2. When losing weight you MUST lift so you can look good after all the fats gone!

So if I'm lifting as part of weight loss, but am on a calorie defecit as well how will lifting help me?

(and I would be lifting even if it doesn't buildbecause I love being strong!)

There's a difference between building mass and building strength. You can and will build strength on a calorie deficit. Building significant mass on a calorie deficit is basically impossible unless you've got one of those freak physiques and metabolisms. Definitely weight train.

Some people can and do build muscle while they're in a calorie deficit.

For example, these people lost an average 16.3 pounds of fat and gained 9.5 pounds of lean mass in 14 weeks:
http://www.thefactsaboutfitness.com/research/build-muscle-calorie-deficit.htm

But it's a phenomenon that's generally limited to people who are very overweight and have never lifted weights before, or those who are returning to exercise after a layoff, where muscle memory comes into play.

For people outside of those categories, lifting weights a) helps to preserve muscle mass/strength during weight loss and b) burns extra calories, which contributes to weight loss.