Singed is very good tank. He's very usefull in teamfights beacouse he's got much healt, armor, magic resist and he can deal much magic damage to all enemys in teamfight.

He's AP tank so he need armor ,magic resist and any ability power. Armor help him with top lane beacause on top are champions who are tanky or AD. Magic resist is mostly to teamfights in late game cuz most of mid laners are AP and ability power runes used to deal more damage.

This masteries only encreas ability power, your health and armor.

Summoner spells:

Ghost is best summoner spell for singed to mobility.
Ignite is best offensive summoner spell on him.

Abilities:

Poison trail is his most offensive spell. Mostly of player LOL mean "Singed is weakest champion in this game" but this isn't true. His magic damage is very large on your lane(top). Poison trail deal 22/34/46/58/70 (+30% Ability Power) per second.
Mega adhesive slow your target by 35/45/55/65/75% (lasts 1 second after leaving). This abilitie rest on the floor 5 sec.
Singed flings an enemy over his shoulder, dealing 80/125/170/215/260 (+75% Ability Power) magic damage.
Singed drinks a potent brew of chemicals, granting him 35/50/65 Ability Power, Armor, Magic Resist, Movement Speed, Health Regeneration, and Mana Regeneration for 25 seconds.

If you want to kill someone run your Q(poison trail) + ghost when you catch your target throw him behind you by E(fling)

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PROS:

[*] Tanky + his passive converte mana to health
[*] Deal much magic damage
[*] Good in teamfights
[*] High CC

CONS

[*] Need much mobility
[*] He must be tanky
[*] Hungry to mana