Answer:
You fill it and it empties, A metaphor for plenty, Depending on what half you see, It's either full or empty
Without what would everyone lose their head?
MT_TF_S What are the missing letters? Why?
Each morning I appear to lie at your feet, all day I follow no matter how fast you run. Yet I nearly perish in the midday sun.
You could do this to a motion, see it on a watch, or place this in a race.
What is lighter than what it is made of?
Easy
Animal
Difficult
Food
Funny
Kids
Logic
What am I?