That can't be good. The most common suspect is probably the anti-sway bar link. That is not serious. A loose brake pad is also not terribly serious. That rattle will stop when you apply a little pressure to the brake pedal. Worn control arm bushings or a worn strut will cause reduced handling and increased tire wear. Play in a ball joint or tie rod end can turn real serious real quickly if ignored long enough. The best course of action is to have the steering and suspension systems inspected at a tire and alignment shop.