When summoned, Guile will remain crouched in one place, frequently throwing his Sonic Boom special at enemies. When an opponent gets close he will immediately perform his Somersault Flash Kick. This odd habit seems to be in reference to a common playstyle that Guile players use throughout the series.
Guile is a Captain of the US Air Force and is frequently hunting down the evil Shadaloo warlord M. Bison in an attempt to avenge the supposed death of his friend Charlie Nash, although as seen in Street Fighter II, his quest for vengeance leads him to abandon his wife Jane and his daughter Amy, though in his arcade ending, they convince him to come back home, telling him that killing Bison won't bring Charlie back, and that it'd make Guile a murderer.
Guile continues to oppose Shadaloo's activities throughout the series and frequently works with Interpol officer Chun-Li.
As mentioned in Palutena's Guidance for Ken Masters, he and Guile are brothers-in-law thanks to their respective wives (Eliza and Jane) although the two Street Fighters cannot stand one another.
Official artwork of Guile in Super Smash Bros. Ultimate.