The fuel.

Love is selfish,
Love is cruel,
Burns like a fire,
Starts like a duel.
Might break your knees,
Might make you sweat,
The love are knives,
The love is a threat.
The pain is true,
You mend your parts together
With hope and glue.
Love is selfish,
Love is cruel,
The clash of force,
The red and the blue.
And explodes like a fuel.