Never land without a clearance
You might have an open mike.
If you think you have an open mike, say so on the frequency. That way you've informed Tower you have the open mike. They will give you a green light to land, or red for the miss.
If you cannot free the open mike, deselect the transmitter select switch. At least you're not sending out music to the ears of others as you curse the boss.
Whether you have an open mike or not, next time you brief an arrival make sure you brief where the Tower is located. Then you'll know where to look if searching for a green light. Sounds like 20/20, doesn't it.
Kai Tak, Hongkong. Runway 31. Early morning arrival. My mike gets stuck as we transfer to Tower. I try everything to free it. I even bang Boeing's column-mounted PTT a few times.
Our multi-skilled Captain gets engaged. He tries to use his hand mike, fly the plane, put the flaps out himself and generally save the day.
It's getting ugly. I suggest we go-round. He swears and carries like on like an old chook a little more. Music to the ears...
We go round, fly the missed approach, free the mike of its burden. In due course, Departures tell us to contact Tower. We get a clearance to land.
Talking to the Tower later on, they said they'd been flashing the green at us for some time on the first approach.
Lesson learned: brief where the Tower is located.
Finally, if you are NOT in possession of a clearance to land, don't.
This isn't subjective. Look up your manuals. Recall your training. We're not talking about military aviation here, nor emergencies, just plain old boring commercial aviation.
Keep it boring!