Answer:
Small, containing light, You'll need it in the dark, It will provide that spark, and shine into the night. Will light up any pyre, 'Cause it can help make a fire.
These are believed to be found at the end of rainbows
Something we eat, and misspell as meet.
What goes through a door but never goes in and never comes out?
Lots of them make up a word, And lots of words are in them. It's easy when you think about it. A while ago we stamped and mailed them.
Almost everyone needs it, asks for it, gives it. But almost nobody takes it.