For objects:
* Weight: This is the most general term.
* Load: Implies something that's being carried or transported.
* Bulk: Refers to the size and density of something.
For emotions:
* Burden: This is a more figurative term for something that weighs you down emotionally.
* Pressure: Implies a feeling of stress or anxiety.
For other situations:
* Traffic: Can be used to describe heavy traffic flow.
* Rain: Can be used to describe heavy rain.
Example:
* "The weight of the box made it hard to lift."
* "The hikers were carrying a load of supplies."
* "The ship's bulk made it difficult to maneuver."
* "The burden of grief was heavy on her."
* "There was heavy traffic on the highway."
* "The rain was coming down in sheets."
You might also use adjectives like "massive", "ponderous", or "substantial" to describe something that is heavy.