Tutorials
Physics Application - Models
As you can see from the image below, I have a very basic room with only a few lights and a player spawn in it. It doesn't matter how much detail there is in the map you’re looking at, this is just for teaching you how to apply physics to models. Once you have your map in front of you, select the entity tool 
, place it near the ground and select prop_physics as shown below.
Under the "Keyvalues" menu, highlight "World Model", click on browse and go to \models\props_c17. You will see a model called "oildrum001". Double click the model and you will be returned to the Object Properties box. Close this and you should see an entity in the form of an oil drum.
That’s it, easy as that. Try it out in game. You can experiment with different models and properties.
Related:
Example Map
Cr4ig