The authors word choice can affect the tone of a poem because lets say that you had written down "Go find the key" this gives a commanding tone, almost like a ruler telling its guard or something. however, if you said "Go find the key please" it will give off a more sincere tone. "Embark on the mission of finding the key, the kingdom awaits" gives it a powerful, almost fearful tone because it leaves you thinking "what awaits?"
There are tons of examples, I hope this helps you!