Move him into the sun—
Gently its touch awoke him once,
At home, whispering of fields unsown.
Always it woke him, even in France,
Until this morning and this snow.
If anything might rouse him now

 This poem is usually regarded as a  soliloquy , that is the thoughts of the narrator become the text.  However, it could be a soldier speaking to his comrades, attempting to wake their fallen friend.  As the title suggests, this attempt is futile. 
 Recruitment in the First World War was based on placing young men from a village or family in the same unit, so they would sustain each other’s morale. The result was that whole villages or families lost their young men. 
 The mood Owen creates in these first lines is sombre, calm, quiet and peaceful – a stark contrast to the noisy, violent battle that probably preceded it. The image of the sun “gently” touching the dead soldier is vastly different to the harshness of the machine guns or artillery or poison gas that killed this man. Note that the first line ends with a dash, forming a  caesura , so that the reader pauses. The second line begins the narrative that leads to the realisation that the soldier is dead, the'fields unsown being a metaphor for life unfulfilled. 
 This can also be a religious metaphor- “sun” can also be “Son” as in the Son of God. This fallen soldier may have looked to his faith for comfort.