Run artbitrary command on every item in a directory tree in PowerShell?

On Command Prompt I can enumerate all files in a directory tree and run an arbitrary command on all of them with either:

FOR /R %F IN (*) DO @COMMAND-HERE ARGS-HERE

Directories only:

FOR /R /D %D IN (*) DO @COMMAND-HERE ARGS-HERE

What are the equivalent commands on PowerShell?