Gym cardio workouts?

helloonikki

Recently just joined the gym for the first time ever, i'm currently doing 20 mins on most of the cardio equipment each but I just wanted to know what exercises people thought were the best in helping to lose weight?

I am worried that I'll do much at the gym and it will end up being counter productive because I've read on some websites that going to the gym too often and doing too much can cause you to not lose weight as it can effect your metabolism or something (not sure how accurate these websites were).

Thanks again guys.