Welcome to Songwriting Fever
You can publish your lyrics on the lyrics directory
which is only accessible to SongWritingFever.com members, therefore, giving your lyrics more security. If you still want to share them on the forum, you can simply paste the link to your lyrics directory here on the forum.
Finally, regarding the song or lyrics stealing thing a lot of people fear, I will let you know my general opinion below (which I wrote a while ago as a response to some of SWF members):
you really can never be sure that your lyrics will not get stolen!
However, in over 5 years of moderating SongWriting Fever Yahoo! group and 2 years working on this website I've never seen a case where someone's lyrics were stolen....I really believe almost all people in such communities are honest and act in good faith. Thieves do not stand a chance because they are by definition unaccomplished folks who wouldn't know what to do with the work they stole anyways...you see my point?
That being said, to fully protect yourself (meaning to protect your rights to your work in a court of law), you will definitely need to formally copyright your song or lyrics with your country's copyrights office. In USA, this is a very easy process, just visit copyright.gov
All the best