First and foremost I would suggest doing research. A recent study showed that in healthy individuals Metformin had no impact on all-cause mortality and there are potential side effects.

Of course, doing research is hard. Because it isn't really research in the sense of running a legitimate study, it's research in the sense of studying the work of others as an outsider.

Personally, I like Dr Brad Stanfield. https://www.youtube.com/c/DrBradStanfield

He's not afraid to reverse positions, he's articulate, he calls out when research is or is not compelling and explains why.

Again, personally, I expect the number one thing you can do to improve your healthspan is probably focus on what you can stop putting in your body vs what things you can add. If you're 40+ though, might be worth looking at other options.