Matthew McConaughey Is Straight Fire Filming 'The Beach Bum'

Matthew McConaughey was barely recognizable Monday on the set of his new flick, "The Beach Bum" ... although the role doesn't look like much of a stretch.

Matt's down in Miami shooting the new flick where he plays Moondog ... a dude who "lives life by his own rules." We smell some serious method acting. Isla Fisher is also in it, but her look's more apocalyptic than beach-y.

Saying McConaughey was born to play this role would be an understatement.

Remember, the man's already got his Oscar ... he can take whatever role he wants.