Is metronidazole 500 mg prescribed for herpes 2?

No, it is not used for herpes. METROGEL-VAGINAL (metronidazole) is indicated in the treatment of bacterial vaginosis (formerly referred to as Haemophilus vaginitis, Gardnerella vaginitis, nonspecific vaginitis, Corynebacterium vaginitis, or anaerobic vaginosis). It is also used to treat Trichomonas vaginalis which is a protozoan. Some of these can be sexually transmitted infections but they are not the same as herpes simplex Type 2. Herpes is a virus as Marvell noted.

Metronidazole is an antibiotic, that fights bacterial infection and would not treat a herpes infection.

Herpes is a viral infection so you would need anti-viral medicines.

The information in the following link may help.

https://www.drugs.com/drug-class/antiviral-agents.html

https://www.drugs.com/cg/oral-herpes-simplex.html

https://www.drugs.com/health-guide/genital-herpes.html