Metal,
Not flame you, but you're 18. How long have you been lifting? How much time have you spent in a gym? No. Not the high school gym and not Balleys. I mean a professional gym with pro athletes. Watch, ask questions, and learn.
Machines isolate the muscle it was designed to exercise. They are designed to duplicate the exact movement of free weights. Plus, there is a built in measure of safety in them.
I'm not trying to argue about free weights v. machines. Both have thier merrits.
If you've seen any of my posts, my philosophy is what works for you, be it lifting, eating, suppliments, or even drugs, is what works for you. You should keep it up if it works.
Fyi; I'm 40 years old, started lifting in high school, and competed in body building locally in the 80's. I am now more into extreme type sports; running, biking, canyoning, etc... I am in the gym every day, doing something... Just re-newed my membership at the same gym for the 14th year in a row!