It is generally appropriate to say "good morning" when meeting someone for the first time if it is morning or during the early part of the day. This greeting is commonly used as a polite and friendly way to acknowledge the time of day and to start a conversation on a positive note.
However, if you meet someone later in the day, it would be more appropriate to use a different greeting based on the time of day, such as "good afternoon" or "good evening."
Remember, cultural norms and practices may differ, so it's always a good idea to be aware of the local customs and greetings when interacting with people from different regions and cultures.