Your first oil change is very important. Get it done on time or, preferably, ahead of schedule. This is because, on a new engine, the block walls, underside of the valve covers, all the head surfaces exposed to oil, the rods, crank, pistons, cam, lifters, etc will shed debris. Most of this will be fine particles, but in some cases, with aluminum heads and block, the factory cast processing can result in rather large pieces of relatively thin aluminum coming loose. As the aluminum flows into the mold it can splash against the wall of the mold. This results in a very thin coating of aluminum on the mold wall then as the mold fills, the casting obtains its full/final shape. But this initial splash can result in a foil like piece of aluminum that can at some point over the miles break loose. If it makes its way to the oil pan it can get pulled into the oil pump. The gears will pulverize this piece of aluminum into a bunch of tinier pieces. These end up in the filter. If the stuff remains in the pan, some can flow out when the oil is drained. And of course where there are sliding, rotating metal surfaces separated only by a very thin layer of oil, this will certainly remove any loose particles of metal. (This is part of the "break-in" process.) Also, besides the accumulation of particulate matter, there is the contamination of the oil. Specifically, water. Old oil can hold up to 7% water. In a Hemi engine with a 7 quart capacity, this can equal almost 1/2 quarts of water. So a word to the wise, don't delay changing your oil!