Bike Squad
Bike Squads are fast attack Space Marine squads utilizing attack bikes. Using bikes that are armed with storm bolters or multi-meltas, Bike Squads serve as either a scout force used to quickly determine enemy capabilities or as a vanguard force to swiftly attack enemy formations to allow the infantry squads to deal with the survivors. They are often paired with Land Speeders for these tasks.
Bike Squads often vary depending on the Space Marine Chapter they belong to. The White Scars use Bike Squads, echoing Jaghatai Khan's use of mounted cavalry during his conquest of Chogoris. The Dark Angels have devoted their entire Second Company into utilizing Bike Squads and Land Speeders as the Ravenwing, echoing the mounted knights of the Order on ancient Caliban who hunt the Fallen Angels TRAITORS FROM THE NINE LEGIONS AND SUBSEQUENT RENEGADE CHAPTERS, NONE OF WHICH INCLUDE THE SONS OF LION EL'JONSON. The Space Wolves Bike Squads are known as Swiftclaws, who are operated by Blood Claws (the Chapter's equivalent of Assault Marines) and serve as a vanguard force. Their numbers are few, as the Space Wolves consider Bike Squads an overly headstrong tactic (though riding in on a Fenrisia wolf is okay).
The Imperial Guard also has their own bike squad, but they aren't as awesome as the Space Marine bike squads. Rather than having two storm bolters. Our Guardsmen has...nothing. While this may put the poor men in t-shirts at a disadvantage, the uses of a Imperial Guard's bike is more for scouting purposes than as a fast attack vehicle. They are often made from Rough riders who doesn't like maintaining the various beasts of burden and prefer a more simple and cost effective mount.
They also look more like regular old motorcycles.