Do weapon damage types have any extra effects?

Question

How do elemental damage types affect a weapon?

For example let's say I had a regular great-axe that ended up doing 10 damage. But, some other guy had a Flaming +1 great-axe that did 10 fire damage. What would be the difference other than fire damage having synergy with a few feats?

Like does the fire damage do some damage over time? Does it brighten up the room? In the PHB1 it has the following descriptions but what do they really do in terms of combat?

• Acid: Corrosive liquid.
• Cold: Ice crystals, arctic air, or frigid liquid.
• Fire: Explosive bursts, fiery rays, or simple ignition.
• Force: Invisible energy formed into incredibly hard yet nonsolid shapes.
• Lightning: Electrical energy.
• Necrotic: Purple-black energy that deadens flesh
• and wounds the soul.
• Poison: Toxins that reduce a creature’s hit points.
• Psychic: Effects that target the mind.
• Radiant: Searing white light or shimmering colors.
• Thunder: Shock waves and deafening sounds.

Answer 1

A weapon that does fire damage does fire damage. A weapon that doesn't do any particular kind of damage does untyped damage.

That's it. They don't do anything magically extra.

Damage type matters for two reasons:

• Synergy with other features which care about damage type: powers, feats, class features, etc.
• Enemy resistances and vulnerabilities.

You're already aware of the former. The latter means the damage of the burning great-axe will vary sometimes, depending on whether the enemy has vulnerable 5 fire or resist 5 fire. The weapon dealing untyped damage, on the other hand, will deal consistent damage against a variety of enemies, because very little resists untyped damage. However, when you do run into something resisting untyped damage — some creatures have "resist 5 all" which includes untyped, and the Grick (MM1) resists effects which target AC — the fire and untyped weapon will still be equal to each other.

Fire damage does not mean anything extra will happen, like lighting people on fire. Certain powers might do that by applying "ongoing 5 fire damage (save ends)", and a particular flaming great-axe like Pelor's Burning Hate might have a power to do that, but that's just the power doing its thing and not a property of the damage type.

Whether a fire weapon lights up the room is a matter of flavour that's outside the scope of the 4e rules, but that would probably be some pretty awesome flavour to explore. I wonder what psychic weapons would do.