NFE Steel Trapper (Magnemite) @ Electrium Z  
Ability: Magnet Pull  
EVs: 4 HP / 252 SpA / 252 Spe  
Modest / Timid Nature  
IVs: 0 Atk  
- Magnet Rise  
- Thunderbolt  
- Hidden Power [Fire]  
- Flash Cannon
Optional Move(s): 
- Hidden Power [Fighting]
- Volt Switch
Optional Item(s): 
- N/A
Optional Ability: 
- N/A
Optional EV/IV(s):  
- N/A
Overview: Magnemite has a small but useful niche as a Magnet Pull Steel-type trapper. It is capable of trapping most standard sets of Metang, Ferroseed, Pawniard, Klang, and Lairon, which means it provides good support for setup sweepers and cleaners such as Clefairy, Sliggoo, Metang, Klang, Staravia, and Trumbeak. However, it is really only useful as a Steel-type trapper, and often provides very little in a game if there is no Steel-type on the opposing team. It is outclassed by Electabuzz except as a trapper.
Modest Steel Trapper: The Modest Steel Trapper set hits harder with its Z-Move and attacks. However, it is slower than Staravia and speed ties with Machoke, which makes it much less useful in games without a Steel-type. Magnet Rise gives it an immunity to Ground-type attacks for 5 turns, which lets Magnemite avoid being OHKOed by Earthquake and subsequently lets it eat a few hits from the likes of Metang and Lairon. Magnemite's Gigavolt Havoc hits even defensive Metang, Pawniard, Klang, and Lairon sets hard and often OHKOs or 2HKOs these Pokemon in conjunction with an unboosted Thunderbolt. Hidden Power Fire hits Ferroseed hard and prevents Ferroseed from recovering enough health with Leech Seed. Flash Cannon is a useful secondary STAB attack which hits Clefairy for good damage.
Timid Speed Trapper: The Timid Steel Trapper set does not hit as hard. However, it outspeeds both Adamant Machoke and defensive Staravia, which means it can fire off a strong Gigavolt Havoc in games where it does not need to trap a Steel-type Pokemon.
Checks and Counters: Marshtomp completely walls and takes advantage of Magnemite. It is immune to Thunderbolt and tanks all other hits. Specially defensive walls such as Roselia, Servine, Quilladin, and Vibrava also comfortably wall Magnemite. Any reasonably strong faster attacker can OHKO or revenge kill Magnemite since it is very frail.