Known as the Devourer of Worlds, Galactus has always had a large presence in the Marvel Universe since he was first created by Jack Kirby and Stan Lee and appeared in Fantastic Four #48 back in 1966. After the Watcher warned the Fantastic Four of the god-like Galactus, he arrived on Earth hellbent on consuming the planet as he had done many times before.
A constant mainstay that has made up Galactus' long history was to provide varying god-like powers known as the Power Cosmic to a scout, or herald, to help find him planets that would satisfy his intense hunger. The most popular of these is the Silver Surfer, aka Norrin Radd, who first appeared in the very same issue of Fantastic Four in 1966. Though he may be the most recognizable of the heralds, there are many other ones that casual fans may have forgotten about. In fact, several of them are characters Galactus could introduce to the MCU.
Destroyer
First appearing in Journey into Mystery #118 from 1965, the Destroyer is an enchanted suit of armor that was first created by Thor's father, Odin, to protect Earth against any foes. The armor was then sealed in the Temple of Darkness until it could be freed once again.
The Destroyer came to be Galactus' herald after his previous one, Firelord, asked to be released from his role. Galactus agreed to this only if they were able to find a suitable replacement. This led to a great idea by the mighty Thor, suggesting Destroyer as it is a mindless and faithful shell. Thrilled by the idea, Galactus agreed to the plan and released Firelord as he took Destroyer along with him.
Morg
Morg the Executioner first appeared in the pages of Silver Surfer #69 in 1992. He was a bloodthirsty and violent warrior who Galactus chose to replace his other herald, Nova. Upon meeting Galactus, Morg said he did not care about his home planet or its people, but that did not mean he would go without a fight.
Galactus thought this compassionless killer would be a better suited herald to search out planets for him, but was disappointed with Morg's violently unpredictable nature and had his powers removed. Without the Power Cosmic, Morg did not survive long and was later killed by the former herald, Terrax.
Human Torch
Brother of Sue Storm and one of the Fantastic Four, Johnny Storm, aka the Human Torch, has battled against Galactus before, but was forced into his ranks when Galactus turned him into one of his heralds in Fantastic Four #519.
During the "Rising Storm" storyline, Galactus originally sought to use Sue Storm as his herald so he could find hidden invisible planets with her powers heightened by the Power Cosmic. In a detail about the Invisible Woman only comic book fans know, Reed Richards (aka Mr. Fantastic) actually switched her powers with Johnny's. The idea behind the switch was to buy them some time to come up with a plan before Galactus could succeed, but Galactus simply captured Johnny instead.
Doctor Strange
Those who may not be up to date on their recent Marvel Universe history will find it interesting that the Sorcerer Supreme has joined the list of scouts under Galactus' rule during the events of Doctor Strange #13. With the Devourer of Worlds banished to the mystic realm, Stephen Strange knew the giant could not stay there in fear he would evolve into something much worse.
As Strange tried to come up with solutions to this problem, Galactus continued to absorb magical entities in the realm to suppress his hunger. Without any other option, Strange agreed to become Galactus' herald so he could find sustenance for Galactus that would not threaten all life. However, Galactus soon triggered a collision of magic and science that began to untangle all of reality.
Sabertooth
A foe of the X-Men and more especially Wolverine, the mutant known as Sabertooth made his first appearance in Iron Fist #14 in 1977. A popular villain, Sabertooth emerged from the panels and onto the big and small screen, portrayed by such actors such as Liev Schreiber and Tyler Mane.
As presented in an alternative universe, Sabertooth was given incredible power by a more peaceful Galactus, defending him against an evil version of the Silver Surfer. In this world, Galactus was able to restore planets instead of destroy them. This violent Silver Surfer demanded that his former master repair his fallen planet, which brought the Surfer and Sabertooth into combat.
The Fallen One
Though Silver Surfer may have been the first herald introduced to the world of comics, he was not actually the first scout for Galactus. The being known as the Fallen One first appeared in Thanos #11 from 2004, but there has been very little information revealed about this early herald.
The Fallen One tried on more than one occasion to kill his former master, but was unsuccessful each time he attacked the powerful Galactus. This desire has even brought him into battle against the Mad Titan Thanos and Star Lord, who was able to finally imprison him for a time before The Fallen One's death.
Dazzler
Marvel mutant Dazzler first appeared in The Uncanny X-Men #130 in 1980 and was created by Tom DeFalco and John Romita Jr. Not only a member of the X-Men and other Marvel teams, Dazzler is actually a pop star who has the power to transform sound into light, with increasing volume creating a stronger output.
In Dazzler #10, she is abducted by Galactus and recreated into a new herald in order to find his escaped herald, Terrax. Terrax had used the Power Cosmic to instead rule over a planet instead of helping Galactus find a world to devour. Angering his master, Terrax escaped into a black hole that only Dazzler was able to enter due to her power.
Aunt May
For those who don't know, Aunt May is the aunt of Peter Parker, aka Spider-Man, and widow of the deceased Uncle Ben Parker. Aunt May first appeared in the pages of Amazing Fantasy #15 from 1962, the very same issue that first introduced Spider-Man to the world. But even some hardcore Spider-Man fans may not know that Aunt May gained the Power Cosmic.
While Aunt May was babysitting young Franklin Richards at the circus in Marvel Team-Up #137, Galactus attempted to turn Franklin into his new herald. With the intervention of Aunt May, she is suddenly transformed into Golden Oldie. To save Earth, Golden Oldie proceeds to gather every Twinkie to feed Galactus. Luckily, the ending to this story showed that it was all just a dream of Peter Parker's.
Willie Lumpkin
First appearing in the world of comic books in Fantastic Four #11 in 1963, Willie Lumpkin is a retired mailman who once delivered mail to the infamous Baxter Building where he had frequent run-ins with the Fantastic Four. Willie even made an appearance in the 2005 Fantastic Four movie, where he was played by none other than Stan Lee.
In the alternate storyline series What If?, issue #34 from 1982 showed only a single panel gag showing Willie as a herald of Galactus delivering a letter to the Fantastic Four from his master, informing them that their planet will be eaten tomorrow. Willie can be see waving goodbye as he floats away with his mail bag.
Superman
In an unusual Superman crossover that will never be seen on screen, Marvel team the Fantasic Four came face to face with the DC hero after Superman was told it was Galactus who destroyed his home planet of Krypton. Superman traveled to the FF's universe in hopes of bringing the villain to justice.
A great point that is brought up at the beginning of the story is that, in the Four's universe, Superman is a pop-culture figure, one that is beloved by the Sue and Reed's son, Franklin. Upon arrival in the Marvel universe, Superman is absorbed by Galactus' device and emerges as a golden herald. After fighting against the Fantastic Four, he eventually is reminded of who he is and helps to stop Galactus, learning the truth about the destruction of Krypton.