How we cite our quotes:
Not marble, nor the gilded monuments
Of princes, shall outlive this powerful rhyme (1-2)
These images of tomb monuments share the purpose of this sonnet: they are works of art that try to sneak past death by lasting a long time. The people they memorialize may be long dead, but marble isn't going anywhere anytime soon. But the speaker one-ups this by creating something that will last even longer: what he calls a "powerful rhyme." It's ripped and it's ready.
But you shall shine more bright in these contents
Than unswept stone besmear'd with sluttish time (3-4)
If you were Time, you might want to sue for libel after seeing yourself described in line 4. In order to attack it more efficiently, the speaker personifies time: in other words, he gives it human characteristics. Instead of being an abstract enemy, time is now more like a messy chambermaid who forgot to do enough sweeping this week. Don't get us wrong—it's still disturbing to read about stone "besmear'd" with all the grossness of passing years—but it's also humanizing. Time is disgusting and dirty. We can deal with that. And the speaker keeps it clean by steering clear of material art and making his poetry abstract and pure.
When wasteful war shall statues overturn,
And broils root out the work of masonry (5-6)
These lines are mostly about violent war, but these "broils" are not described as specific conflicts. Instead, they're vague, universal disasters that seem to concern the whole world's future. Statues and buildings may look like they're built to last, but after a certain amount of time, human violence will catch up with them.