If Goldbug, Humanity's Ally dies before combat damage is dealt to attacking Humans, the damage won't be prevented. For example, this can occur if Goldbug is blocked by a creature with first strike.

The convert keyword action functions the same way as the transform keyword action found on some other cards; to convert a permanent on the battlefield, turn it over so that its other face is up.

The cost is an alternative cost, so it can't be combined with any other alternative costs. It can be combined with any applicable additional costs.

A spell cast this way enters the battlefield with its back face up.

If you copy a permanent spell cast this way, the copy has the characteristics of the card's back face, even though it isn't itself a double-faced card.

To determine the total cost of a spell, start with the mana cost or alternative cost (such as a More Than Meets the Eye cost) you're paying, add any cost increases, then apply any cost reductions. The mana value of a spell cast using More Than Meets the Eye is determined by the mana cost on the front face of the card, no matter what the total cost to cast the spell was.

The mana value of a converted permanent on the battlefield is equal to the mana value of the card's front face, no matter which face is up.

While it's a creature, the Vehicle has its printed power and toughness.

"More Than Meets the Eye [cost]" means "You may cast this card converted by paying [cost] rather than its mana cost." It functions in any zone from which the spell can be cast.

When you cast a spell using its More Than Meets the Eye ability, the card is put onto the stack with its back face up. The resulting spell has all characteristics of that face.

Any triggered ability of another card that triggers whenever a permanent transforms will also trigger whenever a permanent converts.

If a static ability of another permanent applies only to noncreature permanents, that ability applies to a Vehicle with living metal only during your opponents' turns. For example, if you control Arcee, Acrobatic Coupe and March of the Machines, Arcee will be a 2/2 artifact creature during your turn and a 3/3 artifact creature (because its mana value is 3) during each opponent's turn.

"Living metal" means "As long as it's your turn, this permanent is an artifact creature in addition to its other types."

The same is true if it converts before combat damage, so be careful with that second spell!

Similarly, an ability of another card that instructs you to "transform" one of these cards will cause you to convert it, even if that ability doesn't use the word "convert."

Converting a permanent doesn't affect any Auras or Equipment that are attached to it. Similarly, any counters on the permanent will remain on that permanent after it converts. Any continuous effects from a resolved spell or ability will continue to affect it. Any spells or abilities on the stack that target a permanent continue to do so after that permanent converts.