Wow? You can start by actually typing the words "free music download" in the search box. Your very question comes up just about every day. If you want free music (and are too lazy to read the answers posted every time this question comes up here, which is a few times a day) then read.
You have some options.
You can buy the music online at legit sites like iTunes. If you don’t have an iPod, you can use any number of free programs to convert the mp4 to mp3. The problem is that much of the stuff on pay sites is covered by DRM that limits what you can do with it.
You can rip music from CD’s – helpful if your local library is stocked, or you have friends that share your tastes but are okay with paying for them.
You can stream music from an internet radio station through your PC, then use a program like Audacity to record that stream as an MP3 or wav file. You can scan through that recorded stream looking for the songs you want, then copy that part of the stream containing the desired song to an excerpted copy of the larger stream (audacity handles this as well).
If you must use peer-share, you run the risk of infecting your pc by 1) downloading the client program, because it may have viruses; 2) visiting the webpage that hosts the program, because it may contain malware of its own & 3) downloading the media which (in peer-share) comes from other users. No Peer-Share system can guarantee the safety or quality of its media.
I’d avoid Limewire and its variants. I tried limewire a few weeks back after years of happy reliance on winmx and emule. It was nothing special – downloads weren’t fast, selection wasn’t great.