@Cucoo
Niether would be dangerous to a Spartan's MJOLNIR armor. The armor can survive temperatures well over 20,000 F (the temperature of reentering Earth's atmosphere).
As for electricity, EMPs won't work and lightning would have little to no effect, even if their shields were down. Titanium on its own is highly resistant to heat and electricity.
There is one way, but that's for you to find out.
Here's a hint. What do bullets, energy swords, and knives have in common?
Here's their Applications. I had to hunt them down earlier.
Spoiler
(Jack) Spartan-728

Height: 7' 2"
Weight: 1,400 lbs
Abilities: Spartan-V. Similar to that of a Spartan-II. The only difference is that he is slightly weaker in all areas compared to a Spartan-II.
Weapons: Spoiler
Fully Automatic Shotgun (Bullet Storm): The Fully automatic Shotgun is more like an assault rifle than a shotgun, but it uses 12-gauge ammunition. He likes to use explosive shells. This bastardization of rifle and shotgun was created by Dr. Halsey as an improvement to the AA-12. The shotgun also doubles as a rifle. It uses .50 Caliber armor piercing, high-explosive rounds. The shotgun has technology similar to the XM25. The user can program the shells to explode after a certain distance, killing soldiers trying to hide behind cover. That being said, Spartan-728 likes to make them all explode after putting multiple shells inside of his victims...
25mm Grenade Launcher: This 25mm Grenade launcher is pretty much your average grenade launcher, except for the fact that it fires the grenades twice as hard as a normal one. This allows the grenade to embed itself into someone's body before exploding. It was developed by Dr. Halsey as a way to send grenades through armored cars, but it also works very well for people too. This was first discovered by Spartan-728. He has scratched the name "Big Daddy into the butt of the launcher and often uses that as its name.
M6D-MX Magnum Pistol: The M6D Mark X Magnum Pistol is a modification of the M6D used by Spartan-IIs. This pistol is capable of firing 12.7x40mm M225 Armor-Piercing High-Explosive Rounds and can shred through the Ceramic Titanium armor on a Scorpion tank. This weapon's advantages over the old M6D is its higher muzzle velocity. This causes the weapon to give the bullet more force, allowing it to do more damage to its target. This also allows the explosion to be more severe, allowing the shrapnel to travel faster and cause even more damage to its target. This gun was developed by Dr. Halsey as a means to defend against rouge Characters. The M6D-MX is located on Spartan-728's left thigh.
2 Ceramic Carbide Katanas: These Katanas are made of the same material as a Spartan's bones. They are virtually indestructible and never lose their edge. These are not Spartan-728's most used weapons, but they are his favorite. He is even more lethal with these than he is with his guns.
Ceramic Carbide Combat Knife: This Combat knife is made out of the same materials as a Spartan's bones. It is virtually indestructible and never loses its edge. It is located on Spartan-728's left collar bone.
1 Spartan Laser Arm Module: Spartan-728's right arm is not only armor, but a weapon as well. The weapon is a miniaturized version of the Spartan Laser, but can still do the same amount of damage as the original. Not only that, it also charges its power back up, letting it be fired over and over again. This was Dr. Halsey's attempt at integrating weapon systems into the MJOLNIR armor.
Morality/Personality: Spartan-728 is by no means a nice guy. If he is ordered to kill somebody, he will do so with a smile. He is not bound by fear. In battle, he is merciless and cruel. Despite his faults though, he does follow some kind of moral code of his own. He does have honor. He won't kill innocents and despite his sadistic tendencies, he does have some good in him. It's not very often, but sometimes he'll show some form of mercy, depending on his mood. He's not a robot by any means. He is a person that can still be talked to in a normal way and will on occasion, help those in need.
Traumas: Not known. Not even Daniel knows. That being said, there are times when he seems to go into a trance over seemingly random events.
(Daniel) Spartan-636

Height: 6'7"
Weight: 1,350 lbs
Abilities: Just like Spartan-728, except slightly weaker strength, but faster speed and reaction time, as fast as a Spartan-II. He is very proficient in hand-to-hand combat and frequently uses his blades.
Weapons: Spoiler
2 Fully Automatic .50 Caliber Pistols: These pistols were originally built by Dr. Halsey to quickly take down armored vehicles and tanks. Spartan-636 liked to use them anyway, due to their sheer stopping power. The pistols use armor piercing, high-explosive rounds, just like some of the UNSC's weapons. They can switch from semi-automatic, to full-auto.
Shifter Assault Rifle/25mm Grenade Launcher: The Shifter Assault Rifle is one of Dr. Halsey's new creations. This gun is built to adjust it's barrel interior for various ammunition sizes and types. It can use 9mm to .950 JDJ ammunition and can even use 8-gauge shotgun shells. The gun also comes with a 40mm grenade launcher attached to the bottom of the gun.
2 Titanium Alloy Machetes: These weapons are made out of a Titanium Alloy similar to the MJOLNIR's armor plating.
Ceramic Carbide Combat Knife: This Combat knife is made out of the same materials as a Spartan's bones. It is virtually indestructible and never loses its edge. It is located on the right side of Spartan-636's torso.
3 Thermite Grenades These grenades were developed by Dr. Halsey as a way to melt through tank armor. They are known as "lava in a can", due to the heat that they produce once activated. Once the grenade explodes, it shoots Thermite everywhere in its radius and melts flesh, bone, and metal.
Morality/Personality: Spartan 636 is much more stable than his partner, Spartan-728. They are almost exact opposites. Despite their differences, they both are close friends. Spartan-636 is a serious person, but can also be a laid back individual. He tends to keep Spartan-728 in check.
Traumas: None really. He's pretty much your average person, except for the fact that he's a Spartan-V.