Piston and Valve Contact
There are a few things possible here. The piston crown shows signs of melting which commonly leads to metal transfer from the piston to the cylinder head. The cause of this is over fueling either due to an injector failure of some type or unmetered fuel entering the cylinder. Unmetered fuel can be the result of high crankcase oil levels due to fuel dilution. When this occurs oil ends up in the intake and fed to the cylinders. In a worst case scenario an engine runaway situation can occur and when an engine over speeds the valves can float contacting the pistons.