To increase a weapons level you must use it,the more you use it the more it grows!

Z Buster

Zero's defalt weapon,strengh is ok.

Level One - can have up to three shots on the screen at once.
Level Two - can have up to four shots on the screen at once.
Level Three - can charge a minimum shot.
Level Four - can charge a maximum shot.
Level Five - charge faster

Z Saber

You get this at the first boss fight,you'll be using this alot!

Level One - Basic slash
Level Two - two-hit slash combos
Level Three - three-hit slash combos
Level Four - charge slash(stronger)
Level Five - faster charge
Level Six - can perform an aerial spin attack.
Level Seven - can perform a new dashing spin slash.( dash then hit down and b)

Advanced moves:

Press Down + B while dashing to perform this attack. (Level 7)

Spin - Hold B in the air to make Zero spin around holinding out his saber damaging anything in the way, can hit multiple times.

Triple rod

Level One - single stab.
Level Two - Extended Reach, two-hits stab combo.
Level Three - More Reach,three-hit stab combos.
Level Four - can charge the staff.Zero Spins the Rod above his head,looks cool!
Level Five - charge faster.

Advanced moves:

Jump then hit Down the then attck to stab downwards, can hit multiple times.

Shield/Boomerang

Gotten after the 4th mission by the servo,When used it protects Zero from small attacks,it can also be charged then throwen as a boomerang.While charging most of Zero's moves can't be used.

Level One - can charge the boomerang.
Level Two - larger range when thrown.
Level Three - even larger range when thrown.

Elements

Not a weapon but upgrades for them.
They are equiped in the weapon menu,and when you use a charged attack it adds an effect.
Element fonts are gotten by certian bosses.Some enemies/Bosses are weak against certain Elements

Elecric- Shocks enemy,stuns for a short time
Fire- Burns Enemy
Ice- Freezes enemies (not bosses)