There was a pretty good thread about this recently: What happens in AA meetings
Much of that experience is AA in the US. I attend AA regularly. Every meeting/group will be different. If you use the little magnifying glass above to search for “meetings,” there are even more links to read through.
A reminder I was given here that helped a lot for my first meeting: An Open Meeting may be best at first, maybe the volunteer already recommended something though? And there is no expectation or requirement that you will speak or introduce yourself. If asked, it’s okay to pass. It’s totally okay to go and just listen.