Towards the end, during the final battle scene, Magneto wraps the X-Men up in steel girders. Whenever they show a closeup of the X-Men struggling against the girders, you can see them wobble like they are made out of rubber.
I think I'm going to go with Anna on this one. Though I did think that about the rubber at first...when I watched it the second time it did look more like it was loosely connected.
The Ties that Bind were held there by the super-human magnetic type powers that course through Magnito's body. When he left the building, the bars were no longer connected magnetically to the rest of Ms. Liberty, so they bent easier.
Correct me if I'm wrong but I'm sure copper does not react to magnetism. To prove my point take a copper coin and try to pick it up with a magnet - It won't work. Since that is the case, how can Magneto have any power at all over the statue since it is almost entirely Copper.
Magneto does not use magnetism. They only call him the master of magnetism because he can manipulate any type of metal. Which is commonly known as magnetic.