How to check collision

How do I check if one object collides with another without using the trigger function or collision function
Thanks

Would be nice to know, about every other physics api has a way to iterate through current collisions but i havnt found any way to do that with unity.

Physics.OverlapSphere/Physics.OverlapCapsule/Physics.OverlapCube.

Overlaps will get you whats under a given shape against the bounds only. It wont actually tell you wants colliding