Ask HN: Is it okay to ask for more work at your job?

Title might seem ridiculous but it's an honest issue I've been having. I'm new at my current job but it's in an industry that I know very well using tools I know very well.

I'm on top of my main function but if I just focus on that I can go for days without doing anything.

I guess I'm worried that if I ask for more work management may start wondering why they need me in the first place. Can anyone with experience on either the management side or the asking side chime in?