What would you say if you wanted to add information To a dialogue?

I guess it depends on what the dialogue is about. If it was about the weather, I'd probably talk about how changeable the weather is where I live. If it was about politics, I'd talk about what's going on with politics. If it was about quantum mechanics, I'd talk about that. I wouldn't really talk about something the dialogue was about, though, such as talk about quantum mechanics if the dialogue was about weather.