Go easy on me, this is my first post here and I know the answer gets a little weak towards the last few lines :)
I'm not sure if this still counts but:
Originally your riddle started with "ehy you" - Au is the symbol for Gold.
So are you a
I resemble the title of a spy movie
A famous James Bond movie is Goldfinger.
I'll try my best to make you a bit looney;
Refers to a gold doubloon or the Canadian coin called a loonie.
pretty and slick, there is always a con,
Gold is pretty and slick, but can lead to greed
in the wrong hands I sure weight a ton;
When gold is stolen in movies it's often tons of it
You'll know I have many brothers if you are a reader
There are many other types of coins, but not sure about the reader part. Maybe in fiction, gold coins are often the currency of other societies?
they are my followers, I am their leader;
Again, other coins exist, but gold coins are the "best"
Centuries old, not a scratch on my skin,
Gold has been used as currency for hundreds of years and still is the standard
and when I get angry you'll fret for your kin;
Money is the root of all evil