What happened to the tombs when Jesus died, according to Matthew?

Answer: They broke open

When Jesus yielded up His spirit, the earth quaked, rocks split, and the tombs broke open.

“When Jesus had cried out again in a loud voice, He yielded up His spirit. At that moment the veil of the temple was torn in two from top to bottom. The earth quaked, and the rocks were split. The tombs broke open, and the bodies of many saints who had fallen asleep were raised.”— Matthew 27:50-52 (BSB)