The word "throat" is a metonym for everything that people say that is unrighteous and disgusting. Here "open grave" is a metaphor that refers to the stench of the evil words of the people. (See: [[rc://en/ta/man/translate/figs-metonymy]] and [[rc://en/ta/man/translate/figs-metaphor]])
Here "poison of snakes" is a metaphor that is used to represent the great harm of the evil words that the people speak. The word "lips" refers to the words of the people. AT: "Their evil words injure people just like the poison of a venomous snake" (See: [[rc://en/ta/man/translate/figs-metaphor]] and [[rc://en/ta/man/translate/figs-metonymy]])