What Am I Riddles

Question: Each morning I appear to lie at your feet. All day I will follow no matter how fast you run. Yet I nearly perish in the midday sun. What am I?

Question: I can run but never walk. Wherever I go, thought are close behind me.

What am I?

Question: I am a big threat to humanity,
but you wouldn't get rid of me even if you could.

What am I?

Question: I stand in one place yet I fill a whole room.
I can be filled with molten rock and come in every hue.

What am I?

Question: Half of those who read this riddle, I am your best friend.
I depend on you, but it's you I will defend.

What am I?