Mettus was a minor antagonist in Star Trek: Enterprise novel Live By the Code.
A Denobulan, he was the son of Phlox, who would become a prominent Starfleet physician. While his father tried to raise him not to be prejudiced against Antarans Mettus rejected those views. The two eventually became estranged for a number of years. While Phlox tried to reach out to Mettus in 2153 but Mettus ignored his father's attempts.
Becoming more extreme in his views over the years, Mettus fell in with other Denobulans who shared his view. When his sister Vaneel married the Antaran Pehle Retab, Mettus and some of his fellow extremists crashed the wedding on Denobula in order to get the affair called off, but was rebuffed.
Mettus later returned and murdered Pehle's father Sohon, a popular Antaran politician. Mettus was arrested by Denobulan authorities, who were considering extraditing him in order to keep the peace between the two societies. An Antaran extremist group called True Sons of Antar kidnapped Mettus, intending to conduct a show trial followed by execution.
Phlox convinced the Antarans to mount a rescue operation. During the rescue attempt Phlox was wounded. Mettus was taken prisoner by the Antarans, and the Denobulans did not contest the imprisonment.
A short while later Phlox visited his son in prison, which was clean and realtively comfortable. By then Mettus had time to think about his crimes and what his prejudices caused him to do. He also managed to reconcile with his father during this time.