One person died when a car, a van pulling a trailer and a lorry crashed between junctions 10 and 10a on Sunday at about 15:00 BST.
Major repair work was needed to the motorway surface with leaking fuel suspected to have caused damage, said West Midlands Police.
The road was closed for about 15 hours with tailbacks to junction 7.
The hard shoulder could remain shut for repairs for two days.
Highways England described it as a "complex recovery operation overnight".
The M6 motorway between Wolverhampton and Walsall has reopened after a fatal crash.