A theme is expected when writing nonfiction
All of the nouns used (hammer, chain, furnace, brain, anvil) are explaining mighty things that the tiger is being compared to. The poem is simply saying that they are smart, speedy, and strong.
I hope this helped! If you have further questions don't be afraid to ask!
~Travis
4 will be the answer for you sir or ma’am
Before buying the 2nd largest house, he lived in Stratford-upon-Avon
