“trees.” The “trees” are people, and in this context it refers to rulers and leaders. This is the commonly-used figure of speech hypocatastasis. [For more on “trees” being people, see commentary on Luke 3:9. For more on hypocatastasis see commentary on Rev. 20:2].
“will be cut down.” Although the present tense verb is used, the cutting will be done in the future. This is the idiom some scholars refer to as the “prophetic present,” and it takes an event that is future but certain to happen and coming soon, and treats it as if it is present. [For more on the prophetic present, see commentary on Luke 3:9.]
“and thrown into the fire.” John is giving these leaders a very serious warning. God expects people to have faith in Him, obey Him and do good works, and those who do not are in danger of being thrown into Gehenna, the Lake of Fire, which is the “second death” and is everlasting death (Rev. 20:14-15). [For more on annihilation in the Lake of Fire, see Appendix 5, “Annihilation in the Lake of Fire”].