Answer:
Consuming food would be pretty tough without these chompers
What is found over your head but under your hat?
What has 4 fingers and a thumb, but is not living?
What gets broken without being held?
A big shiny black car nobody wants to be a passenger in.
I am the fountain from which no one can drink. For many I am considered a necessary link. Like gold to all I am sought for, but my continued death brings wealth for all to want more.