Alcohol and metronidazole interact in a severe or even dangerous way. Even the prescribing information for metronidazole products warn of this possible interaction, stating that consuming alcohol while taking this drug (or even within three days of metronidazole) may cause the following side effects: Nausea; Vomiting; Flushing; Headache; Digestive upset.
https://www.drugs.com/answers/safe-metronidazole-hours-after-drinking-alcohol-586421.html