Lead Bloon

The Lead Bloon is a unique Bloon that was introduced in BTD2. Lead Bloons have also been featured in every subsequent BTD game. Having a unique ability, Lead Bloons are immune to sharp projectiles and the Super Monkey's Laser Vision, since they're made of metal. Identifying Lead Bloons is effortless as they have a metal-like appearance and they are the only gray colored Bloons in the game. Popping a Lead Bloon and its descendants rewards a total of 19 or 23 Money. They first appear on round 28 in BTD5, and two rounds later there are some more. They contain 2 black bloons. In BTD4, They contain 4 black bloons making the RBE of the Lead Bloon to 45

General Strategies
As the description says, it is quite easy to kill leads as long as your strategy is not based off "sharp" towers. Try to include a few explosive or "slow down" towers. Leads are mainly dangerous because of their special ability AND of the abilities of their children and grandchildren. The blacks are immune to most of the explosions popping the leads whereas the pinks are fast enough to avoid most attacks.

Speed
This bloon moves as slow as a red bloon and a M.O.A.B in Bloons Tower Defense 4. However, despite the fact that it's slow, it's still faster than a B.F.B, since the BFB is slower than a red bloon.

Trivia

 * Due to Lead Bloons being introduced in BTD2 and appearing in every subsequent game, players can no Hjhjkhjkhjkhjk.jpgr pass the game with only Road Spikes or Dart Monkeys. However, this is theoretically possible in BTD4 or BTD5 given that the player has the Explosive Darts premium upgrade.
 * It is possible to beat Park Path on Hard in BTD5 with Dart Monkeys only (Daily Challenge #77).
 * Pineapples can pop lead bloons with proper timing.
 * The Super Monkey's Laser Vision upgrade cannot pop lead bloons even though they're not sharp. This is because the bloons are made of metal and metal reflects light.
 * The TV show Mythbusters created a real lead balloon, and despite common assumption, it's biggest problem was not it's weight. The lead was so fragile that it tore during inflation. They also built aluminum balloons, which apart from being an odd shape, worked perfectly well.
 * It is the only bloon to resist physical attacks not by using hit points. It takes one non-physical hit to pop.
 * It is unaffected by Tornado Attacks since they're too heavy.
 * In the iOS version, Super Monkey Laser Vision can pop lead bloons.
 * If you place Road Spikes in front of a Lead Bloon, you can say goodbye to your spikes because lead bloons cannot be popped by road spikes.
 * If you want all of your towers within a radius to all be able to pop Lead Bloons, you can need to upgrade your Monkey Village to Monkey Intelligence Bureau.
 * If you make a lot of Super Monkeys with the upgrade Laser Vision and there is a lead bloon, it will sound like there is a background noise that has a very high pitch. More lead bloons=longer noise (ting ting ting and more tings).
 * The Monkey Apprentice's Tempest Tornado can pop lead but can't move them.
 * Sniper Monkeys can pop leads with their bullets, even though bullets are sharp.
 * A Dartling Gun with the Laser Cannon cannot pop leads but a Ray of Doom can.
 * The Lead Bloon, along with the Z.O.M.G., is the only Bloon that does not have a parent.
 * A single Lead Bloon can go through a fully grown Bloonberry Bush completely unharmed.
 * Robo Monkey's darts and lasers can pop lead bloons.

Links
To see upgrades that can pop Lead Bloons, click here.