Copyright protects an “original work of authorship," including song lyrics, from unauthorized use. Copyright of original work is free and automatic. However, it will be difficult to prove your copyright if it isn't registered with the United States Copyright Office, which charges a fee.
Copyright is automatic as soon as a work is created. For example, as soon as lyrics are written down. The problem is that there is a difference between the legal fact that you own the copyright and your ability to prove this in court. If you want to sue someone for copyright infringement, that is, for using your work without your permission, you will need to show in court that you created the lyrics first. This may be difficult unless you have some type of proof.
Poor Man's Copyright
Some people, seeking to obtain proof that they created a work on a certain date, use a “poor man's copyright." In a poor man's copyright, you mail yourself a copy of your work by certified mail, leaving the envelope sealed. The idea is that you can then unseal the dated envelope in court to prove the work was written on a certain date. The problem with this method is that it may not stand up very well in court. There are ways to fake a poor man's copyright, for example, by mailing yourself an unsealed envelope and then sealing it at a later date. The courts are aware of this and may give very little weight to this type of proof of copyright. Whether it is enough for you to prevail in a lawsuit will depend on your individual circumstances.
Certain organizations like The American Society of Composers, Authors and Publishers, or ASCAP, allow you to register your works online for free. They then license your work, distribute royalties and police for unauthorized use. The U.S. Copyright Office notes on its website that while copyright is automatic, in order to bring a lawsuit for infringement, your copyright must be registered with the USCO. So while these sites will protect your copyright, simply registering your work with them may be not enough to prove copyright in court.
Registering a copyright with the USCO costs $35, as of 2011. However, for this fee you can register any number of lyrics, as long as they were all written by the same person. If you have 100 or more songs to register, you will only pay pennies per song. You can fill out the copyright registration form online. You will also need to submit a copy of the lyrics – this can also be done electronically. It will take a few months to process the copyright, but your work is protected from the day you complete and upload the forms. This is the surest way to protect your ownership of your lyrics.