Note that this guide is based on the MHW beta playtests, there may be updates upon release so be sure to check back.
Weapon Switching Guide (How to Swap)
Overview
For as long as the franchise has been around, Monster Hunter has captured the hearts of many players with their exotic monster designs, lush scenery, cool armor sets, and most importantly badass weaponry!
Each weapon has various movesets with their own feel and each boasts unique gameplay mechanics.
For example, you can stun monsters in the head with the Hammer, shoot health bullets at allies with the Light Bowgun and Heavy Bowgun, parry a monster's attack with the Longsword, and so much more. Each weapon is unique in its own way.
However, every Monster Hunter game only allowed you to bring one weapon during your hunt until now. Let us dive into the newly introduced gameplay mechanic in Monster Hunter Wilds: switching between 2 weapons.

This guide is written by JourneyFar.
How Weapon Switching Works
In the older games, you would only be able to change your weapon back in the quest hub - newer generation games allowed changing weapons during hunts but only in Camp Areas. Now you can have two weapons set, a primary and secondary. This allows you to change your weapon to another right in the middle of a monster hunt!
The only problem is that it can only be done on your mount, the Seikret.

While mounted on the Seikret, press the corresponding buttons to switch back-and-forth between the weapons you chose. It is as simple as that but you do need a bit of time to swap, it isn't instant.
Also, each weapon is capable of a mounted attack while riding the Seikret for additional mobility.
Examples of Benefits
Being able to switch weapons introduces a variety of possibilities and optimizations in every hunt now. With different status effects and elemental properties, switching your weapon can make you feel at ease in every situation. This can reduce hunting times significantly in some cases.

Can't cut a monster's tail off because you're using a Hammer? Switch to a weapon that does cutting damage. Facing a monster that likes to fly around and run away? Switch to a Bow or Bowgun for long-distance fighting.
Maybe your allies are in a pinch? Switch off from your weapon to a Bowgun and shoot some healing bullets at them. Or maybe switch to a Lance to try to tank some hits.
Since the ability is not limited in any way, a hunter can freely switch into the same weapon category like Dual Blades to Dual Blades.
Maybe switching to another pair of weapons with higher sharpness is faster than using a Whetstone now.
In the case of a hunt with several different monsters with different elemental resistances, a hunter can now prepare for it better and waste no time going back to a Pop-up Camp.

Imagine using a weapon that inflicts Blast during the hunt. Each time Blast is inflicted onto the monster the hidden threshold value increases; as in, it now takes even more hits to inflict Blast onto the same monster.
But the monster has never been Poisoned or Stunned yet. So with Weapon Switching, a hunter can now switch to their Poison weapon and start inflicting Poison on it. Incredible!
Final Thoughts
Hopefully, Weapon Switching is a choice rather than an enforced ability. It would be tough to make this mechanic be something forced upon like having a monster that completely negates melee weapons from reaching them. This could annoy players as they are forced to switch to a weapon they are not familiar with and have no interest in. Luckily, for the time being, the mechanic is there only if wanted.
This new mechanic is interesting to say the least. Being able to switch weapons on the fly sounds like a great opportunity to mix up gameplay if it starts getting stale somehow. It is up to us players to see if it will be crucial, detrimental, or just a nice touch to add to the game.