This is a metaphor. Poisonous snakes are dangerous and represent evil. This could be translated as "You evil poisonous snakes!" or "You are evil like poisonous snakes." (See: [[rc://en/ta/man/translate/figs-metaphor]])
This phrase begins a rhetorical question. John was rebuking the people because they were asking him to baptize them so that God would not punish them, but they did not want to stop sinning. The whole rhetorical question could be translated as "You can't flee from God's wrath like this" or "Do you think that you can flee from God's wrath just by being baptized?" (See: [[rc://en/ta/man/translate/figs-rquestion]])
This could be translated as "from the punishment that is coming" or "from God's wrath that he is about to act on" or "because God is about to punish you." The word "wrath" is being used to refer to God's punishment because his wrath precedes it. (See: [[rc://en/ta/man/translate/figs-metonymy]])