"Metal Boxes" is an infamous line uttered by Chaos Lord Firaeveus Carron, a character in Relic Entertainment's video game Dawn of War: Soulstorm. The line is said when the player playing as Chaos Marines encounter Rhinos while attacking the Blood Raven stronghold. Carron mocks the Blood Ravens for cowardice despite the fact that his own forces also uses Rhinos. The actual line goes as follows:

"Look! Rhinos! RHINOS! Our enemies hide in METAL BOXES, the cowards! THE FOOLS! We… We should take away their METAL BOXES!"

"Metal boxes" is often heard as Metal Bawkses.

Carron's overreaction coupled with the irony made it instantly become a meme among Dawn of War fans, to the point where any mention of "boxes" or even "Rhinos" will result in somebody shouting "METAL BOXES!" on certain forums. 4chan has even produced a Metal Boxes song:

"METAL BOXES on the hillside,
METAL BOXES full of Spess Mehreens!
We must crush them 4 teh BLOOD GOD,
All the RHINOS must be burned!
There’s a Drop Pod and a Whirlwind
And a Dreadnought and a Predator,
But I’d rather smash the RHINOS,
METAL BOXES DIE TODAY!!!

All the foolish little Spess Mehreens
Think they’re safe in transport vehicles,
Well they’ll find it hard to hide when
THERE’S AN AXE SHOVED IN THEIR BRAINS!!!
All their tactics and their transports
And their STEEL REHN and their FUREH
Cannot stand the power of Chaos,
We shall take their tanks away!

Bash the RHINOS, smash the RHINOS!
I hate them more than anything!
They’re the reason Mummy hates me,
They’re the cause of all my pain!
Just look at me, I’m an ugly mess,
And my voice acting’s hammy,
This whole game is fucking awful,
And the RHINOS caused it all!

METAL BOXES on the hillside,
Destroy them, my minions!
We shall shoot them with our Bolters,
We shall tear them into scraps!
They are cowards, they are weaklings,
An offence to the BLOOD GOD!
And they’re made out of adamantium
AND THEY ALL MUST DIE TODAY!!!!!"