Yes, you walk through metal detectors and they search everyone's backpack, purse etc. As they should. They make sure you and everyone is safe. Disney security is on point. During the parade 2 years ago a fight broke out between 2 dad's. Security was there in under 3 seconds. They have people in the crowd in plain clothes. It was spectacular to watch them break it up, remove them from the area then have someone come over in a cartoon costume (Pluto) and recreate the mood in under 30 seconds. If your metal cup is just that, you'll be fine. Not sure why anyone needs a metal cup at Disneyland but okay. You and your bags will be searched. If it passes muster, you're fine. Enjoy the park. They take better care of their guest then anyone else in the world.
My family takes sports bottles when we visit, no problem. If it's Just a metal cup not a sports bottle type they may reject it.
Yes you can
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