Moves that cause the user to faint, Destiny Bond, and Perish Song can still cause a Pokémon with Magic Guard to faint.
Source
Moves like Explosion, Self Destruct, and Misty Explosion causes the user to faint, so Magic Guard won't prevent a Pokemon from fainting after using Explosion.
Here's a replay of Magic Guard not preventing Reuniclus from fainting after using Explosion.
However, Mind Blown works like Steel Beam, so having Magic Guard prevents the 50% HP loss.
Mind Blown inflicts damage, and the user takes damage equal to half of its maximum HP rounded up (unless it has Magic Guard).
Source
Replay of Magic Guard + Mind Blown interaction.
TL;DR Explosion, Self Destruct, and Misty Explosion causes the user to faint if the Pokemon has Magic Guard, while Magic Guard prevents the 50% HP loss from Mind Blown.
(Also, Sucker Punch doesn't get boosted because it was known as "Surprise Attack" in Japanese)