Is it safe to take these pills together (metronidazole 250 mg) and (omeprazole 20 mg)?

No interaction. Although there is no known significant interaction for these two medications, caution is always advised using combo meds. If you must take the medicines, pay attention to your body, as u get older u r more prone to side effects which u may not have when younger etc.. Take medication in smallest effective dose and shortest time possible. When in doubt, consult your doc. Good luck.
Usually. Those two drugs can usually be taken together with no problem! some people, however, metabolize things differently through liver pathways (genozyme test) like cyp 2c19 or cyp 2d6. Some people are slower (drugs can build up and cause side effects) or faster (drugs go through to fast and don't work right). It is important to know these when being treated for any psych conditions!