Minecraft wiki entry for Materials, associated text: Endermen teleport depending on materials that block movement. They choose a random destination and then seek downward until they find a block with a movement-blocking material.
Various things that spawn on the "surface" similarly check material movement-blocking to find the surface.
Paintings, banners, signs, cakes, and item frames are placed on any solid material. This is why signs can be placed on each other without any visible connection.In addition, paintings and item frames can also be placed on the sides of the redstone comparator and repeater.
Player spawning checks for obstruction based on whether the material is solid or fluid, apart from banners, pressure plates, and signs.
Cacti break depending on the solidity of an adjacent block's material and whether the adjacent block is lava or whether the material of the upper block is liquid.
Farmland and dirt path turns to dirt if a solid-material block is placed on top, except fence gate. But moving piston can be placed on farmland.
Water and lava spread and currents generally depend on whether the block's materials blocks movement, while placement from a bucket depends on whether the material is solid or replaceable, except end portal and end gateway.
When above a block with a replaceable material, the gravity-affected blocks can fall.
Only blocks with a solid-blocking material can be redstone conductor.
Iron golems can be spawned in air or liquid materials above a solid-blocking-material block whose collision-box has a square upper surface by villagers.
When broken, ice becomes water if above a block with a liquid or movement-blocking material.
Lava checks for a flammable material nearby when attempting to start fires. The fire itself uses its own list of flammable materials, which is why fire can start next to a wood block without consuming the block.
Block with a movement-blocking material and a full cube collision causes suffocation.
Various tools check for materials to get breaking speeds.
Rain and snowfall fall through blocks that have a non-liquid material that does not block movement.
Dungeon, lake, and nether portal generation checks for solid materials, rather than solid blocks.
Note blocks check blocks or materials to determine some instruments. They check for a material of stone, sand, glass, and wood, with the resulting instrument being the base drum, snare, glass, and bass, respectively.
Various blocks with different variants check the material to determine what sounds to play.
Doors and trapdoors often use the wood and metal materials to differentiate between wood and iron doors and trapdoors.