The song in the promo for the CBS crossover event of Hawaii Five-0 and NCIS Los Angeles is "Dark Horses" by Switchback.
Visit their website for more infos about the band.
Hear an acoustic version of the song...
Dark Horses
I've made my mistakes
I've seen my heart cave in
I got my scars
I've been to hell and back again
Born for the blue skies
We'll survive the rain
Born for the sunrise
We'll survive the pain
We're singing hey, you can't count us out
We've been running up against the crowd
Yeah, we are the dark horses
We're singing wait, it's not over now
We've been down but we've never been out
Yeah, we are the dark horses
We found a way out
The city takes everything it can
But outside the crowds
I can feel my lungs again
Born for the blue skies
We'll survive the rain
Born for the sun rise
We will survive the pain
We're singing
La la la la la la la
Were singing we don't care what they say
We know we'll find a way
Yeah, we are the dark horses
Keep running with the dark horses
Stand up for the dark horses
Hope makes the blood change courses
Keep running with the dark horses
Stand up for the dark horses