You could raise your shield and have the guardian destroy the shield but deal no damage to you, and you could also parry while your shield is raised to reflect the beam back. BotW had a parry button you could use while your shield was raised.

The Guardian and Ancient shields would auto-reflect beams, but still consume shield durability. Any shield could be used with the parry and not consume durability. (This goes for most if not all monster attacks.)