An officer may come to your home to interview someone in an investigation; to make a notification or give a message; or to serve an arrest or search warrant.
A search warrant is a judge's court order commanding officers to search a location for evidence or a person. A copy will be left at the house and a list of property taken given to the homeowner. The homeowner need not be home when police serve a warrant. You may ask to see a copy of the search warrant.
It is not necessary for the officer to have a copy of an arrest warrant in hand with them in order to make a valid arrest.
Police officers will provide identification and their reason for being at your home. However, when executing a warrant, police do not have to "knock-and-announce" if they believe there are emergency circumstances. This would include protecting a life or preventing the destruction of evidence