How to stop thinking about metaphysical questions?

I have been practicing seriously for a month now. I'm mindful a lot of the time but not 100% yet and whenever I'm not I start thinking about metaphysical questions or what could be after death or if it is nothing etc. How can I stop this? Or how to stop thinking about something in general when you don't want to? For some reason I can't be equanimous with metaphysical questions. They run through my head like there's no tomorrow and nothing more important than that. It's quite annoying. Would noting help?