You're really not suppose to delete META-INF as that tells java what class file to launch primarily (So you can easily do java -jar filename.jar), nothing is affected though since Forge has its own meta-inf folder that it needs, so it'd be overwritten anyways.
An easier step would to just have the Forge Zip and the Server jar in the same folder and run the Forge zip file. (java -jar MinecraftForgeZipFile.zip), then you don't have to copy Forge into the jar.
Its an extra step skipped