Why is the Metallica Cover song I uploaded (nothing else matters) no longer on my profile? I uploaded it a few weeks ago and now it is not there. Should I upload again?
It's a cover. It is not allowed here.
When you change a song, you even need the "okay" from the artist or the label. In case of a 1:1 cover you don't need that permission, but you have to pay some money to the GEMA....most clubs or bars (especially with bands playing) have deals with that institution. Magix doesn't - it wouldn't make any sense anyhow.
You really should read the Terms and Conditions at the bottom of the screen. In it they state:
"MAGIX stores the photos, videos, music and information ("Contents") for the customer or solely grants access to them. The customer alone is responsible for the contents on the MAGIX servers as well as the domains chosen and the name of his/her email address. The customer guarantees that these do not violate any legal prohibitions, are not contra bones mores or against third parties (name, trademark, personal, copyright, data protection rights etc.)."
ALL music written and published after 1921 (in the USA anyway) is protected by copyright laws, which do not expire until at least 75 years after the composer's death. In other words, they are likely to be in effect even after you die.
Just because you have been able to avoid any legal issues so far does not mean you are safe. These laws can be enforced by the copyright holders at any time.
Even someone as young as 19 should know that Metallica takes their rights very seriously.