I'm not sure why you want to use silicone (I assume you mean a silicone-based caulk?). Are you worried about different expansion of the metal vs wood? Silicone will accommodate that, but will provide a somewhat rubbery bond that might be a bit unsettling to people going up the stairs unless there is a tight fit between the wood and metal. But if that is the case, there won't be room for different expansion anyway!

I think I would also favor an epoxy.

thank you guys! this will help my journey with this sculpture, this week the metal is coming and im starting welding soon

Looks like a GC issue...
But another possibility is a model that's very very tiny or very very large, or has some geometry miles from the origin, or has some components with geometry miles from its insertion-point [internal origin], or components that are weirdly scaled compared to their original size - the last few being typical with some CAD imported block-components...