Honestly, anything that shows off your vocals works in a talent show. Choose the song based on what works best with your vocal range. And stay away from songs over 3 minutes. This girl at our talent tunjuk had an AMAZING voice but people got bored after she hit the 4 minit mark on Halo.
I think anda should sing something in your vocal range with notes that are easy for anda to reach and hit. And also something that anda have the lungs to sing based on how soft atau intense your voice is. Pick a song that anda can understand emotionally. And tempo is important, too; don't pick something too fast atau too slow.
Well, I don't know if you're into this kind of Muzik but link is an amazing song with amazing lyrics too. In case you're not comfortable with symphonic metal (well, this song is not metal really, at all) an acoustic version could work too. Anyway, other really good bands are Indica and VersaEmerge. Hope this helps!
So in my opinion anda really should do a song that anda know and love. sejak that I mean knowing the lyrics but if anda don't have one of can't hit those really high notes here are some it mainly depends on what type of Muzik anda like if anda like pop do maybe pity party, never forget anda etc. atau if anda are into country do little toy guns, picture to burn, blown away etc.