Editing Warhammer 40,000 (section)

===Assembling armies===
All the models that a player has selected to use in a match are collectively termed an "army." In ''Warhammer 40,000'', players are not restricted to playing with a fixed and symmetrical combination of game pieces, such as in chess. They get to choose which models they will fight with from a catalogue of "datasheets" presented in the rulebooks. Each datasheet corresponds to a particular model and contains any relevant gameplay statistics and permissible attachments. For instance, a model of a [[Space Marine (Warhammer 40,000)|Tactical Space Marine]] has a "Move" range of 6 inches and a "Toughness" rating of 4 and is armed with a "boltgun" with a range of 24 inches. Both players must declare which models they will play with before the match starts, and once the match is underway, they cannot add any new models to their armies.

In official tournaments, it is mandatory for players to only use Games Workshop's models, and those models must be properly assembled to match the player's army roster; substitute models are forbidden. For example, if a player wants to use an Ork Weirdboy in their army, they must use an Ork Weirdboy model from Games Workshop.<ref>{{Cite web|title=Model Requirements for events at Warhammer World|url=https://warhammerworld.warhammer-community.com/wp-content/uploads/sites/15/2019/10/Updated-Model-Requirements.pdf|url-status=live|archive-url=https://web.archive.org/web/20220118092623/https://warhammerworld.warhammer-community.com/wp-content/uploads/sites/15/2019/10/Updated-Model-Requirements.pdf|archive-date=2022-01-18|access-date=2022-02-02}}</ref> Games Workshop has also banned the use of 3D-printed miniatures in official tournaments.<ref>{{Cite web |last=Baer |first=Rob |date=2021-05-26 |title=Games Workshop Opens the War Against 3D Artists |url=https://spikeybits.com/2021/05/games-workshop-opens-the-war-against-3d-artists.html |access-date=2022-07-13 |website=Spikey Bits |language=en-us |archive-date=2022-07-13 |archive-url=https://web.archive.org/web/20220713183757/https://spikeybits.com/2021/05/games-workshop-opens-the-war-against-3d-artists.html |url-status=live }}</ref> Public tournaments organised by independent groups might permit third-party models so long as the models are clearly identifiable as to which ''Warhammer 40,000'' model they are meant to represent. Tournaments might also have rules regarding whether armies are permitted to be used unpainted or must be painted to a certain standard.

The composition of the players' armies must fit the rivalries and alliances depicted in the setting. All models listed in the rulebooks have keywords that divide them into [[#Factions|factions]]. In a matched game, a player may only use models in their army that are all loyal to a common faction.<ref>'' Warhammer 40,000'' (core rulebook, 8th ed.), p 214</ref> Thus, a player cannot, for example, use a mixture of Aeldari and Necron models in their army, because in the game's fictional setting, Aeldari and Necrons are mortal enemies and would never fight alongside each other.

The game uses a point system to ensure that the match will be "balanced", i.e., the armies will be of comparable overall strength. The players must agree as to what "points limit" they will play at, which roughly determines how big and powerful their respective armies will be. Each model and weapon has a "point value" which roughly corresponds to how powerful the model is; for example, a [[Space Marine (Warhammer 40,000)|Tactical Space Marine]] is valued at 13 points, whereas a Land Raider tank is valued at 240 points.<ref>'' Warhammer 40,000: Index: Imperium 1'' (8th ed.), p 202</ref> The sum of the point values of a player's models must not exceed the agreed limit. If the point values of the players' respective armies both add up to the limit, they are assumed to be balanced. 500 to 2,000 points are common point limits.

Although the rules place no limit on how big an army can be, players tend to use armies comprising between a few dozen to a hundred models, depending on its faction. A large army will slow down the pace of the match as the players must physically handle many more models and consider each strategically. Larger armies also cost more money and take more work to paint and assemble.