Although much of the game can take place offline through a single player mode, the most content is contained in the online section of the game. Most monsters, with the exception of a number of higher ranked monsters, or specific variations, are available to fight via single player mode. However, the same monsters can be fought online, usually ending with items of greater value or rarity not attainable through single player. Goals for players online are not to defeat the most monsters, but to reach the highest hunter rank, which is the "semi-storyline" that is carried out online by NPC characters.
Monster Hunter is played through quests given to the hunter by the Village Elder or the Town Guild. Quests can be classified into four categories: hunting, gathering, capture and event. They are also categorized into different levels, ranging from 1-8*. A newer level quests become available after certain quests of the previous * are completed.
Hunting quests make up the majority of the missions. As the name implies, the hunter will track, provoke, and eventually slay a monster or a number of monsters using various equipment including: Barrel bombs, pit traps and much more (many quests require specific equipment pieces to be completed). As the hunter progresses, the monsters will become more difficult, but will provide better materials for the hunter to utilize.
Gathering quests are missions in which the hunter must "gather" items. These items can be as simple as herbs, to as complex as pieces of a monster or ore from a mine. These quests give out the least amount of reward, but sometimes give valuable items.
Capture quests can be the most difficult to complete due to a certain degree of restraint that must be shown by the hunter. The hunter must bring the wyvern to a certain degree of damage, but not kill it (this can usually be seen by the wyvern limping). After the wyvern shows signs of physical weakness, it must be captured by snaring it in a Pitfall Trap and putting it to sleep. A captured wyvern cannot be carved since it is still alive, but the rewards are significantly rarer and the reward money is generally greater. Contract fees for Capture quests are high, but not as high as some of the rarest hunting quests.
The Event quests are an online-only feature. Every week, a new Event quest is available to hunters of any rank. These quests vary in style and difficulty. Some of the rarer weapons can be made only through Event quest rewards. Event quests are not vital to a hunter's success in the game, but are a useful way to gain experience and to obtain some rare items. Contract fees and time limits vary.
All of the quests allow two deaths, but the third death marks the failure of the quest. Regardless which player actually dies, three deaths will still fail the quest. The only exceptions to this rule are some of the Event quests, which are failed with just one death.
- Apceros, a desert-dwelling, herbivorous, Ankylosaurus-like Reptile.
- Aptonoth, a common, Parasaurolophus-like cousin of the Apceros.
- Bullfango, a long-tusked Suid. Herd leaders are called Bulldromes (which will be seen later in the series).
- Cephadrome, a large, fearsome, carnivorous Piscine Wyvern with a Diplocaulus-like head. A youngster is called a Cephalos. A very odd-looking Dragon.
- Diablos, a very large, extremely dangerous, omnivorous Flying Wyvern with an axe-shaped tail, two large forward-pointing tusks and horns over the eyes as well as a bony head frill like that of a Triceratops. It is found in deserts.
- Fatalis, a dark-purple Dragon that breathes fireballs that can kill a Human in an instant.
- Felyne, one of two intelligent, Cat-like Lynians. This type is colored like sand.
- Genprey, a desert-dwelling, vicious, pack-hunting, Dromaeosaur-like Bird Wyvern that cannot fly. Pack leaders are called Gendromes.
- Gravios, one of the largest Wyverns. It has a resemblance to a stone statue. A juvenile is called a Basarios.
- Gypceros, a poisonous Bird Wyvern with a very strangel-shaped, beak-like mouth.
- Hornetaur, a Neopteron Insect resmbling a combination of a Beetle and a Cricket.
- Ioprey, a red cousin of the Genprey that lives in volcanic regions. Pack leaders are called Iodromes.
- Kelbi, a common, Antelope-like Deer. Males are green and females are blue.
- Khezu, a large, Leech-like Wyvern that lurks in caves and has no eyes.
- Kirin, a white, Unicorn-like Creature with red eyes. It is in the group of Monsters known as Elder Dragons (same group as the Fatalis).
- Lao-Shan Lung, a gigantic, wingless Elder Dragon with an appearence like a combination of an Armadillo Lizard, Godzilla and a Chinese Dragon.
- Melynx, one of two intelligent, Cat-like Lynians. This type is dark-colored and is more mischievious than the Felyne.
- Monoblos, Monoblos ruber, a cousin of the Diablos that is also a desert-dweller. It is omnivorous like the Diablos and it has a very Styracosaurus-like head.
- Mosswine, a Pig with a Pachycephalosaur-like dome and a symbiotic relationship with Moss and Mushrooms.
- Plesioth, a large Piscine Wyvern with a Shark-like head. It swims in a very unique fashion.
- Rathalos, a red-colored Flying Wyvern that looks like a very typical Dragon with the ability to breath fire. A female is gray-green, weaker and called a Rathian.
- Velociprey, a blue cousin of the Genprey and Ioprey that is more common than them. Pack leaders are called Velocidromes. The name is a reference to Velociraptor.
- Vespoid, a large and dangerous Wasp. Leaders are Vespoid Queens (which will be seen later in the series).
- Yian Kut-Ku, a omnivorous, Pterosaur-like Bird Wyvern with large frill-like ears that dwells in swamps and jungles.
- Poogie, a pig-like beast that has been featured in every MH game to date.