Yes. Many engine rattles can be fixed quickly and affordably. The most common reason for engine rattling is a collapsed valve lifter. This needs to be repaired quickly or it can cause misfires. Other common causes that need immediate attention are a failing tensioner belt, drive belt or low oil pressure. If the rattle is intermittent, it may be a poor connection between the rod and the crankshaft.
If the noise is loud, it may be a cracked flex plate or rusted heat shield. Higher mileage vehicles may have an engine rattle resulting from an engine hotspot ping, piston slap or degrading sound dampening features such as engine insulation. Sometime what sounds like an engine rattle is not the engine at all but a cracked catalytic converter.